There has been a surge in the number of EPTB cases in recent times (2). Share of EPTB as a proportion of total number tuberculosis [TB] cases in USA has increased from 7.6 in 1962 to 15.7% in 1993, and to 21.0% in 2006 (3-5). Bone and joint tuberculosis accounted for 5337 (11%) cases out of a total of 47,293 cases of EPTB reported in USA from 1993-2006 (6). In the absence of a reliable epidemiological data and very sparse published literature, it is not possible to give an exact figure on the relative contribution of EPTB to the total number of TB cases in India (1, 7). Bone and joint tuberculosis constitutes 10-11% of total EPTB cases which would be approximately 1-3% of all TB cases (8, 9).
MSK-TB is usually classified into Spinal TB and TB of peripheral joints (10). Spinal TB constitutes nearly 50% of all MSK-TB (11). The other relatively uncommon forms of MSK-TB are Poncet’s disease (para infectious TB arthritis), TB soft tissue rheumatism, and iatrogenic rheumatism and TB osteomyelitis (10). TB of the spine and peripheral joints has been covered in the chapter “Skeletal tuberculosis”. The main focus of present chapter will be on an overview of TB arthritis, Poncet’s disease [para infectious TB arthritis] and TB soft tissue rheumatism.
AETIOPATHOGENESIS AND PATHOLOGY
Though there are various species of Mycobacterium tuberculosis complex like M.tuberculosis, M.bovis, M.africanum and M.microti, the causative agent of MSK TB almost always is M.tuberculosis (11). The causation due to the other species is very rare. Infection with M.tuberculosis occurs through inhalational route, ingestion or direct inoculation (12). Particles less than 5 ?m can pass through the natural protective mechanisms in the airways and carry 1-5 mycobacteria (12). These numbers can result in infection in an immunocompromised host like infant, elderly, and comorbidities like diabetes, hematological malignancies, immunosuppressive therapy and HIV etc (12). De novo infection depends upon the ability of the mycobacterium to escape the host defenses like alveolar macrophages [pneumocytes] and delayed hypersensitivity (12). There is an intracellular multiplication of mycobacteria with the help of toll like receptor-2 and complement binding receptors, mannose, cholesterol related receptors, and CD14, leading to burst of pneumocytes (12). The released mycobacteria are phagocytosed by other macrophages triggering a chain reaction resulting in cytokine production, inflammatory response and eventual hematological spread (12). There is development of protective immunity mediated by CD4 lymphocytes with the help of CD8 cytotoxic lymphocytes and B cells (12). Several virulence factors of the mycobacterial cell wall like cord factor, lipoarabinomannam (LAM), and 65-kDa heat shock protein [hsp65] also play a role in the pathogenesis. Various cytokines such as interleukins, interferon gamma and tumour necrosis factor ? [TNF ?] play a protective role against TB infection (12). These are responsible for formation and maintenance of granuloma. This is important for containing and killing mycobacterium. TNF ? are being increasingly used in various rheumatic diseases like rheumatoid arthritis, spondyloarthropathies etc. There is a risk of reactivation of tuberculosis in these individuals and it might be due to disruption of TNF dependent cellular migration necessary for maintaining the integrity of the granuloma (12).
The MSK TB infection is mostly secondary to hematogenous spread from a primary focus, which may be in the lungs, lymph nodes or other organs and that source can be demonstrated in up to 40% of these patients with the help of sensitive imaging modalities like MRI (13). The joint infection is usually a result of either spread from a TB osteomyelitis or seeding of the synovium from due to the hematogenous spread. There is synovitis in the initial stage of infection, followed by formation of granulation tissue and pannus in the later stages, which eventually results in cartilage destruction (13). This is followed by demineralization and necrosis resulting in severe bone damage. There may be formation of para articular cold abscess [without signs of inflammation] and external fistulae (11).
Host genetic factors do play a role in susceptibility to TB (14). Various studies have shown associations of different genetic polymorphisms with either increased or less risk of development of tuberculosis (15-16). EPTB like MSK TB is predominantly a disease of the children and young adults in endemic areas. In the non endemic areas, it affects people with older age or some form of immunocompromised state (17-18). People with HIV infection, diabetes mellitus, and on immunosuppressive and cytotoxic therapies are at increased risk of TB (19-23). Patients on treatment for underlying rheumatologic diseases like SLE, RA or gout may also develop MSK TB (24-27). There may be TB involvement of the prosthetic joint also (28).
The clinical manifestations of MSK TB can be divided into four major categories (29): [i] Direct MSK involvement; [ii] Development of TB during treatment of rheumatic disease; [iii] Effects of antituberculosis drugs; and [iv] Reactive phenomenon
Direct MSK Involvement
Typical TB infection presents as a slow, smoldering localized infection of the bones [osteomyelitis], spine, peripheral joints and soft tissue. Since the spinal and peripheral joint involvement has been discussed in other chapter, only a brief overview of the tuberculosis arthritis is being provided in this chapter. TB osteomyelitis seen both in children and adults, but is more common in children, and may involve any bone. Femur and tibia are the most commonly involved bones, though ribs skull, phalanx and other bones may also be involved (12). In children, TB involvement of the phalanx may cause dactylitis and present as a diffuse ‘spindle like swelling of the finger’ (11).The overlying skin is shiny and stretched. Radioisotope bone scan may show ‘hot spots’ in the metaphysis of a short bone of the hands and feet (11).
Joint involvement is usually in the form of chronic monoarthritis of the large and medium weight bearing joints like hip and knee (30). Clinical manifestations are in the form of pain and swelling of the involved joint along with restriction of movement. Constitutional symptoms in form of fever and weight loss may also be present. Other joints like sacroiliac, shoulder, elbow, ankle, carpel and tarsal joints are less commonly involved. Polyarticular or oligoarticular involvement is uncommon. There may be a polyarticular involvement in a debilitated child or adult with a past history of TB or TB contact (11).The presentation mimicking juvenile idiopathic arthritis has also been reported rarely (31).
The soft tissue TB infection can present as tenosynovitis, bursitis, myositis or fasciitis. There may be a delay in diagnosis of these conditions when there is a resemblance to focal soft tissue inflammatory conditions (32).
Myositis is uncommon condition and the usual causative organism is Staph aureus (33). TB myositis is even rarer. Most of these patients have predisposing conditions for TB (34). The proposed mechanism of involvement is thought to be due to either a ‘hematogenous’ spread, ‘contiguous’ spread from the adjoining bone and soft tissue or ‘iatrogenic’ due to direct inoculation through contaminated instruments (34). Abnormalities on chest radiographs have been noted in up to half of these patients. Though rare, this has been reported to have significant mortality rate of around 14 per cent with even higher mortality [30%] in patients with possible hematogenous route of infection (34). The clinical presentation is in the form of local signs and symptoms of inflammation.
Development of TB During Treatment of Rheumatic Disease
Many patients with active inflammatory rheumatologically disorders receive various immunosuppressive drugs, making them susceptible to reactivation of tuberculosis. Though anti TNF therapy and corticosteroids are most commonly incriminated agents, all patients who receive any immunosuppressive therapy affecting the cellular immunity should be considered at risk of reactivation of tuberculosis (37). Data from a large patient registry reported a TB incidence of more than 1000 per 100,000 patient years of exposure to TNF blockers (38). This rate was reported to be 6 cases per 100,000 in patients with rheumatoid arthritis before the starting of widespread use of TNF blockers (38). Etanercept may be associated with relatively lower risk (39). This reactivation is mostly 6-12 months after initiating the TNF blockers, and is usually in form of EPTB. Proper screening for latent TB in these patients results in decrease in active TB (40). Glucocorticoids also increase the risk of reactivation in patients with latent TB infection. Though the risk appears to be dose related, it is the even in patients on low physiological dose of prednisolone 7.5 mg/day.
Effects of Antitubeculosis Drugs
Drugs used in TB treatment can produce various clinical conditions. Isoniazid and Rifampicin may produce drug induced lupus. These patients have ANA and anti Histone positivity. The disease is generally mild and reverses on stoppage of these drugs. Fluoroquinolones especially ciprofloxacin and levofloxacin have been associated with tendon rupture (37). This risk is higher in older individuals, and those on corticosteroids. Pyrazinamide can cause hyperuricemia due to interference with renal tubular excretion but this rarely results in gout (37).
Reactive Phenomenon (Poncet’s Disease)
This is a form of inflammatory arthritis without any evidence of direct TB involvement of the joint in the presence of TB elsewhere in the body. This was described by Poncet in 1887 in patients with current or past history of EPTB (38). In the absence of any diagnostic criteria, other disease conditions have been included in this diagnosis, and this has led to controversy over this terminology. The definite pathogenesis of Poncet’s is uncertain but is similar to ‘reactive arthritis’ as a result of molecular mimicry between Mycobacterium tuberculosis and articular cartilage. Mycobacteria are arthretogenic. A CD4 T cell response to mycobacterial antigens is has been shown to play a role (39). Chronic synovitis resembling rheumatoid arthritis can be produced by injection of complete Freund’s adjuvant [heat killed and desiccated M. tuberculosis in oil]. Arthritis has also been reported as a side effect of the BCG immunotherapy in patients with bladder carcinoma. The description of clinical presentations of Poncet’s in the literature is derived from small case series and case reports (41-48). Poncet’s is more common in juveniles and young adults, with some female predilection. There may be fever and constitutional symptoms in some patients. The pattern of joint involvement commonly described is acute or sub acute symmetrical polyarthritis predominantly involving the large joints like knees and ankles. Symmetrical small joint involvement resembling rheumatoid arthritis has also been reported occasionally. The most common site of TB is pulmonary (49). Most common site of EPTB is lymph nodes (11). TB may sometimes develop during the course of Poncet’s (47). Manteaux test is usually strongly positive except in disseminated TB. Poncet’s is a diagnosis of exclusion and there is no evidence of active TB of the joint; and it resolves completely with anti tubercular therapy.
Panniculitis Associated with TB
Erythema nodosum [EN], the septal panniculitis, is the most common form of panniculitis seen in TB. Panniculitis is a non-suppurative inflammation of the subcutaneous fat without vasculitis. EN is due to delayed type of hypersensitivity reaction to variety of antigens. There may be various causes of EN like infections [bacterial, mycobacterial and fungal], drugs [especially sulphonamides and oral contraceptive pills], inflammatory bowel disease and various rheumatologically conditions like behcet’s disease and sarcoidosis. This may be associated with fever and constitutional symptoms in the eruptive stage. Arthralgia’s or arthritis may be seen in up to half of these patients. The characteristic presentation is in the form of erythematous tender nodules over the shins, which are palpable and often tender. There is induration of the overlying skin. Occasionally, it may be in the form of a sheet like indurated, hyper-pigmented swelling over the ankles and shin. Though any joint may be involved, but ankle, knee and wrist are the most commonly involved joints.
Erythema induratum [EI] of basin type is a lobular panniculitis and has a similar presentation in the form of tender erythematous nodules. These are more commonly seen on the calves but shin can also be involved occasionally. The other sites of involvement are trunk, buttocks, thighs and arms. Unlike EN, which heals without scarring, EI heals with ulceration or depressed scars. This can also be associated with ankle arthritis. EI is one of the three types of tuberculides, the other two being lichen scrofulosorum, and papulonecrotic tuberculide. Tuberculides are result of immunologic reactions to antigenic components of MTB. Histopathology and PCR may confirm TB in some of these patients and these respond to antituberculosis treatment.
UNUSUAL MANIFESTATIONS OF MSK TB
Various types of very unusual manifestations of MSK TB have been reported. Some of these are [a] non healing ulcerated mass resembling a synovial sarcoma due to TB synovitis, [b] hip pain due to trochanteric bursitis due to TB, [c] sternoclavicular mass, [d] bilateral steroclavicular involvement,[e] involvement of great toe,[f] lower end of fibula,[g] midtarsel joints, [h] sternum after sternotomy following bypass surgery (50-55). Bakers cyst has also been reported due to TB (56).
MUSCULOSKELETAL DISEASES ASSOCIATED WITH NON-TUBERCULOUS MYCOBACTERIA
MSK involvement due to non-tuberculous mycobacteria [NTM] are uncommon. Mycobacterium kansasii is the most common NTM species to cause MSK involvement, though involvement due to other species like M.xenopi, M.avium intracellulare, M.chelonei, M.fortuitum has also been reported (57-61). Synovial sheath infection is more common than infection of the osseous tissue (62). Most of these patients have some predisposing conditions though it has been reported in a patient without any apparent immunocompromise (63). These infections have also been reported in a patient with a rheumatic disease like SLE or Still’s disease (64). Arthritis due to NTM has also been reported after exposure to contaminated marine life (65, 66).
DIAGNOSIS OF MSK TB
A high index of suspicion is required for making the diagnosis of MSK TB. Common MSK manifestations are spondylitis or chronic monoarthritis. The cornerstone of diagnosis is the microbiological or histopathological evidence of MTB infection. Patients with risk factors for tuberculosis such as immunocompromised individuals, elderly, and children, those on immunosuppressive drugs must undergo these investigations in an appropriate clinical setting.
Laboratory investigations like elevated erythrocyte sedimentation rate [ESR], C-reactive protein level, are nonspecific. Positive culture is the gold standard. Conventional culture on Lowenstein-Jensen medium takes a longer time [3-6 weeks]. Newer techniques like BACTEC have reduced the isolation time to 2 weeks. Molecular diagnostic techniques like polymerase chain reaction [PCR] or Gen probe are even faster. PCR has been shown to be a good sensitive and specific technique for diagnosis of various extra pulmonary TB conditions including osteoarticular TB; and even for diagnosis of NTM infections like M.avium (67-73). Cepheid GeneXpert MTB/RIF assay is an automated cartridge based molecular diagnostic method which can diagnose MTB infection and rifampicin resistance in one and half hours. It has been not been extensively evaluated in EPTB conditions.
Skin testing, like tuberculin skin test [TST] indicates exposure to the MTB organism, and is a marker of latent TB infection; and may not mean active disease especially in high prevalence countries. Since the purified protein derivative [PPD] used for tuberculin test contains various MTB antigens which are almost identical to Bacille-Calmette-Guerin [BCG] antigens or NTM antigens, TST may also be positive in BCG vaccinated individuals or NTM infected individuals.
Interferon gamma release assays [IGRAs] like QuantiFERON TB gold and T-SPOT.TB have recently been developed to diagnose latent TB infection. These tests use two MTB specific antigens, ESAT-6 and CFP-10 and hence are not affected by BCG vaccination and NTM infections. Synovial fluid aspiration and synovial biopsy are very important for establishing diagnosis of TB arthritis.
Indications of Synovial Biopsy
The issues concerning procurement of adequate tissue for histopathological diagnosis of skeletal TB are discussed in the chapter “Skeletal tuberculosis [Chapter?]. The indications for a synovial biopsy in patients with MSK-TB from a rheumatologist’s perspective are discussed below.
When clinical evaluation and routine investigations fail to provide a diagnosis synovial biopsy is the logical next step. It is usually the only definitive method of diagnosing infection with fastidious organisms including TB. An absolute indication for synovial biopsy is a chronic inflammatory monoarthritis where synovial fluid examination including microbiological studies may have failed to give a definitive diagnosis. Another strong indication for synovial biopsy would be a patient with persistent disease activity in a single joint.
Imaging of MSK TB
Imaging in patients with skeletal TB is covered in detail in the chapter “Skeletal tuberculosis” [Chapter?]. Certain key issues related to imaging in MSK-TB are described here under to supplement the content covered in the chapter “Skeletal tuberculosis” [Chapter?]. Among the various available imaging techniques, computed tomographic scan [CT scan] is superior in depicting the degree of bony destruction and facilitating image-guided biopsy for spinal TB. On the other hand, for detailed anatomical evaluation and for distinguishing different densities of tissues [fibrous tissue, abscess, meninges, spinal cord etc.,] magnetic resonance imaging [MRI] with contrast is considered superior (74). The characteristic ‘Phemister’s triad’ is considered rather typical of TB. Three components of the triad are [i] juxta- articular osteoporosis, [ii] peripherally located osseous erosions, [iii] gradual narrowing of the joint space (75-77). On the other hand, in the course of RA and pyogenic arthritis, the joint space narrowing occurs early. For soft tissue TB, the ultrasonography is the method of choice as it shows the extent and degree of involvement. On the other hand, the MRI shows the extent of soft tissue, osseous and joint involvement (75). One of the other typical features of TB aetiology of the bones that have a relatively superficial cortical surface [e.g., metacarpals, metatarsals, phalanges, tibia and ulna] is the presence of lytic lesions surrounded by reactive subperiosteal new bone formation (13). It needs to be emphasized that despite these advances, the ‘gold standard’ for the diagnosis of TB of the MSK system still remains histo- pathological and/or microbiological confirmation; definitive treatment cannot be instituted before confirming the diagnosis (75).
Treatment consists of administration of standard antituberculosis drugs. Many workers suggest nine months of treatment for extrapulmonary TB including MSK-TB (78). The reader is referred to the chapters “Treatment of tuberculosis [Chapter?] For details.
Recycling Aluminium into Alum Crystals
This experiment was designed to recycle aluminium into alum crystals which have uses in industry. The aluminium was converted to alum by heating the metal samples with potassium hydroxide solution. The product was then reacted with sulphuric acid followed by crystallization. Overall, five trials were conducted with the only variable being the mass of aluminium used. The mass of crystals produced increased until the trial of 0.9g, when excess aluminium was observed. These different aluminium masses consisted of 0.3g, 0.5g, 0.7g and (2x) 0.9g.
These particular research questions will be answered throughout this EEI:
How the mass of the scrap aluminium related to the final mass of the alum crystal?
How can stoichiometry of a sequence of chemical reactions be used to calculate the percentage yield of alum synthesized from aluminium scrap?
How can scrap aluminium be chemically converted into a crystal?
How does converting aluminium to alum make a worthy recycling process (make use in society, is it financially sustainable?).
2.0 Introduction 2.1 Background Information Alum is a salt that in chemistry is a combination of an alkali metal, such as sodium, potassium, or ammonium and a trivalent metal, such as aluminium, iron, or chromium. The most common form, potassium aluminium sulfate, or potash alum, is one form that has been used in food processing.
Modern beverage containers are usually composed of aluminium, in the form of aluminium cans. Australians consumed over 3 billion aluminium cans in 2005. Additionally, approximately 300 million aluminium beverage cans are produced each day in the U.S. Recycling has the benefit of reducing litter from discarded cans and a number of states have passed laws requiring a deposit on aluminium cans to encourage recycling.
In this experiment, instead of recycling scrap aluminium into new metal cans, a chemical process will be used that converts scrap aluminium into a useful chemical compound, potassium aluminium sulfate dodecahydrate, KAl(S04)2 ï‚· 12H20, commonly called “alum”. Alum is widely used in the dyeing of fabrics, in the manufacture of pickles, in canning some foods, as a coagulant in water purification and waste-water treatment plants, as well as in the paper industry.
In an aqueous solution of KAl(SO4)2 ,the K , Al3 , and SO22- are surrounded by molecules of water (they are hydrated). These ions do not have an orderly arrangement in solution. When the compound is forced to crystallize, the ions must begin to join each other in their characteristic order. This process of nucleation may occur spontaneously when the ions of alum collide with appropriate orientation and with sufficiently low kinetic energy to permit them to “stick” to each other and prevent them from rebounding. Occasionally, some foreign solids (irregularity on the wall of the container, dust particles) will serve as nuclei (or starting points) for the formation of crystals. Once a tiny crystal has formed, ions in their random motion through the solution will hit the faces of the crystal, join the orderly array of ions, and make the crystal grow. There is ionic bonding, covalent bonding and intermolecular attractions, plus hydrogen bonding, which is the attraction between water molecules. The only type of bonding not present in potash alum is metallic bonding.CAS_GIF_7784-24-9.gif
Aluminium, like almost all metals exhibits “metallic bonding”. It can be oversimplified by saying that metallic bonding is like having positive metal ions in a sea of mobile electrons. The mobile electrons are the loosely held valence electrons that can easily move from atom to atom.
In fact, metals behave more like atoms which share orbitals to form delocalized covalent bonds. Orbitals from adjacent metals atoms overlap side-to-side to form pi- bonds.
For example, in this diagram, each iron atom, (and the same is true for aluminium) exhibits side to side overlap of the orbitals making pi bonds. Only one axis is shown in the diagram, but overlapping of the atoms in front of and behind this line also occurs. The beauty of this is that the electrons can move along the pi-bonds, from atom to atom, allowing the metal to conduct electricity.
Potassium alum is hydrated potassium aluminium sulfate KAl(SO4)2*12H2O. Since all chemical bonds are essentially covalent in nature, then this compound contains covalent bonds as well. The potassium-sulfate bond is the most polar, and the most ionic-like of the bonds. The substance crystallizes in a face-centred cubic arrangement of hydrated K and Al atoms alternating with SO4 radicals. Despite being a vast oversimplification of a complex structure, there are ionic bonds between K and SO4 and Al and SO4, and there are covalent bonds within SO4. This allows an electrostatic attraction between the polar water molecules and the ions.
Although aluminium is a “reactive” metal, it reacts only slowly with dilute acids because its surface is normally protected by a very thin, impenetrable coating of aluminium oxide; such metals are referred to as self-protecting or passivating metals. Alkaline solutions, or bases, (containing OH-) dissolve the oxide layer and then attack the metal:
AL2O3(s) 2NaOH(aq) 3H2O(l) ———> 2NaAl(OH)4(aq)
2AL(s) 2NaOH(aq) 6H2O(l) ———> 2NaAl(OH)4(aq) 3H20(g)
Thus, in aqueous alkaline medium, aluminium is oxidized to the tetrahydroxoaluminate anion which is stable only in basic solution.
Aluminium is obtained from a raw material called bauxite predominantly in Latin and South America, Africa, and Australia. Recent technological improvements have seen the energy cost of producing one tonne of aluminium drop to 15,000 kW, but that is still a lot of energy on top of which must be added, the energy of transporting the metal obtained around the world. Therefore aluminium recycling is extremely important and very easy for everyone to do.
Because of the energy used during extraction of aluminium from bauxite, aluminium is the only commonly used packaging material with a value that exceeds the financial costs of recycling it. To recycle an aluminium can, it costs only 5% of the energy used to create it in the first place. Additionally, aluminium can be recycled many times without any loss in quality.
2.2 Aim The aim is to investigate the effect of the amount of scrap aluminium on the amount of alum crystal produced when the amounts of potassium hydroxide and sulphuric acid used are kept constant.
2.3 Hypothesis It was hypothesized that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly, when potassium hydroxide and sulphuric acid are kept the same.
3.1 Chemicals Potassium hydroxide, KOH, 1.0 M solution
Sulphuric acid, H2SO4, 6 M solution
3.2 Apparatus Aluminium beverage can
Beakers: 3x 50-100mL, 3x 250mL, 3x600mL
4.1 Variables 4.1.1 Independent Variables Independent Variables are those that are changed on purpose. The Independent Variables of this experiment are:
The mass of the scrap aluminium
4.1.2 Dependent Variables The Dependent Variables are the factors that change according to the independent variables. The Dependent Variables of this experiment are:
The amount of alum crystal produced
The size of the alum crystals
4.1.3 Controlled Variables Controlled Variables are the variables that are kept constant during the entire experiment. The controlled variables of this experiment are:
Amount of potassium hydroxide poured into the beaker
Amount of sulphuric acid poured into the beaker
Same size beakers for all five experiments
4.1.4 Uncontrolled Variables The uncontrolled Variables are those that cannot be kept regular and may affect the validity of the experiment. The uncontrolled variables of this experiment are:
The impurity of the scrap aluminium
4.2 Procedure 4.2.1 Risk Factors Before the procedure can be commenced, certain safety precautions must be implemented prior to the beginning of the experiment. First of all Alum is non-toxic, although alum solutions can cause eye irritation (potassium hydroxide solutions are caustic). Therefore it is crucial to wear goggles or safety glasses when working with the solution. It is essential that the growing solutions are stored in a safe environment and not be disturbed. In the event of contact with skin or eyes (with any of the solutions – especially sulphuric acid which is highly corrosive), the affected area must be washed immediately with lots of water. If necessary, medical assistance should be obtained. Sulphuric acid is corrosive. The aluminium metal may have sharp edges, so it must be handled with care. Before handling any beakers, they must be inspected for any chipped or sharp edges, which may cause injury. Bunsen burners can be very hazardous due to its roaring flame so it must be used with caution. The flame must not be anywhere near the rubber hose because it can be easily melted. As long as all chemicals are kept distant from the human body, the Bunsen burner, and any other dangerously reactive materials, safety will be optimized.
4.2.2 Method A piece of aluminium was scraped with sandpaper to eliminate the strong, thin aluminium oxide layer.
The mass of the clean piece of aluminium was carefully measured; 0.300g ( /- 0.001g).
The aluminium piece was then cut into smaller pieces, allowing larger surface area for the following reaction.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos18052010030.jpg
These smaller pieces of aluminium were then placed in a 250mL beaker, with an added 50mL of 1M KOH (potassium-hydroxide).
A Bunsen-burner was then used to heat up the solution to boiling point, to completely dissolve the aluminium (a stirring rod is useful for enhancing the rate of reaction).
Once the aluminium was completely dissolved, the solution was then filtered using filter paper, removing insoluble impurities.
After being filtered, 20mL of 6M H2SO4 (sulphuric acid) was then added to the solution.
Immediately white crystals began to form in the solution.
The alum was removed from the liquid by filtration.
The alum was then left for 24 hours to crystallize.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos18052010039.jpg
The filtration paper was then placed under a heat lamp to rid any condensation or leftover moist on the paper.
The weight of the final alum crystal was then able to be defined by subtracting the original weight of the filtration paper from the weight of the filtration paper with the alum.
This resulted in a final given amount of produced alum crystal.
REPEATED STEPS 1-13 (x4) with weights of scrap aluminium; 0.5g, 0.7g, 0.9g (2x)
5.1 Tables Amount of alum produced:
Beginning Amount of Aluminium
Amount of Alum Crystal
At temperature, 100 parts of water dissolve (g/100ml):
5.2 Graph Beginning weight of aluminium piece
Amount of alum produced (g)
Starting weight of aluminium
Percentage Yield for alum experiments
Solubility of potash alum in water:
Amount of books containing alum:an17-4a.gif
Consumption and Recycling of aluminium can beverages in the world:
5.3 Experiment Yield Theoretical Yield:
2Al(s) 2KOH(aq) 4H2SO4(aq) 22H2O(l) ——> 2KAl(SO4)2â€¢12H2O(s) 3H2(g)
According to the chemical reaction, 2 moles of aluminium will react to form 2 moles of alum.
Theoretical yield = Mass of aluminium used = Mass of Alum obtained
Molar mass of aluminium Molar mass of Alum
Percent yield = Mass of alum obtained x 100
Theoretical yield of alum
0.300 = X 3.769 x 100 = 71.6
27 474 5.26
The percentage yield is 71.6%
0.500 = X 4.913 x 100 = 56%
27 474 8.77
The percentage yield is 56%
0.700 = X 7.878 x 100 = 61.55
27 474 12.8
The percentage yield is 61.55%
0.9g Aluminium (trial 1):
0.900 = X 8.763 x 100 = 55.46
27 474 15.8
The percentage yield is 55.46%
0.9g Aluminium (trial 2):
0.900 = X 4.437 x 100 = 28.08
27 474 15.8
The percentage yield is 28.08%
6.0 Discussion From the results obtained, it can now be determined how the mass of aluminium affects the alum crystal mass and size. After making all recordings, different qualitative and quantitative results were questioned. As seen from the results obtained in “5.0 Results”, there were two trials for the experiment with the mass of 0.9 grams of aluminium. This was decided because it was apparent that at around 0.9g of aluminium, it would begin to cause the solution to be saturated. Therefore the procedure for these two experiments differentiates in the following way; as with the other experiments, one was filtered after adding the sulphuric acid (creating the alum), and the other was left to crystallize with no further process. These both resulted in a successful and an unsuccessful result, which provided qualitative results. The one that was filtered had completely crystallized within 24 hours. The one that was left in a solution with aluminium was left to crystallize. The alum did not precipitate from this solution. This result was an anomaly for the experiment for it gave dissimilar results which were discarded. The same procedure was successful until 0.9g due to the fact that the aluminium was acting as the limiting reagent. At 0.9g the potassium hydroxide became the limiting reagent allowing the aluminium to serve as the excess reactant.C:UsersGeorgioDesktopSchoolChemistryMaterials Assignment – Yr 11Photos19052010040.jpg
These were all the chemical equations step by step during the procedure:
When sulphuric acid is slowly added to an alkaline solution of this complex anion, initially, one hydroxide ion is removed from each tetrahydroxoaluminate anion causing the precipitation of white, gelatinous aluminium hydroxide, Al(OH)3
2K[Al(OH)4](aq) H2SO4(aq) â†’ 2Al(OH)3(s) K2SO4(aq) 2H2O(l) The excess potassium hydroxide is neutralized by some of the sulphuric acid to form potassium sulfate.
2KOH(aq) H2SO4(aq) â†’ K2SO4(aq) 2H2O(l) On addition of more sulphuric acid, the aluminium hydroxide dissolves forming the hydrated aluminium cation
2Al(OH)3(s) 3H2SO4(aq) â†’ Al2(SO4)3(aq) 6H2O(l) Addition of alkali to the Al(OH)3 precipitate will also bring about dissolution by reforming [Al(OH)4]. A hydroxide, such as aluminium hydroxide, that can be dissolved by either acid or base is said to be amphoteric. When the acidified aluminium sulfate solution is cooled, potassium aluminium sulfate dodecahydrate (“Alum”) precipitates.
Al2(SO4)3(aq) K2SO4(aq) 24H2O(l) â†’ 2K[Al(SO4)2]â€¢12H2O(s) The overall reaction that takes place is the sum of the previous reactions.
2Al(s) 2KOH(aq) 4H2SO4(aq) 22H2O(l) â†’ 2KAl(SO4)2â€¢12H2O(s) 3H2(g) All of the filter papers that were to be used were weighed, and an average filter paper mass was recorded for later purposes. For each of the alum solutions that were produced, once filtered (excluding the one that wasn’t filtered), were then given 24 hours to crystallize before data and measurements were recorded. It was apparent that in the beaker that contained the solution of the filtered alum, there were small crystal seeds that had formed. This was due to the saturated solution which still contained alum, therefore in the 24 hours it was able to grow into bigger alum seeds. The remaining liquid in all the beakers was decanted leaving only the crystals; they were placed under heat lamps for 10 minutes to evaporate any adhering water. Some final results from the measurements were now conductible. Knowing the beaker mass, the beaker mass with alum, the filter paper mass and the filtration paper mass with alum, the amount of alum produced was established. These final crystal masses were:
0.3g = 3.769g ( /- 0.004g)
0.5g = 4.913g ( /- 0.004g)
0.7g = 7.878g ( /- 0.004g)
0.9g = 8.763g ( /- 0.004g) (with filtration paper)
0.9g = 4.437g ( /- 0.002g) (without filtration paper)
It is quite obvious to state that a trend in this experiment was recognized after noticing that (as stated in the hypothesis) when more aluminium is used, more alum crystal is produced, so long as the aluminium remains the limiting reagent. As the aluminium mass increases, the alum product remains at a fairly relative mass for all four scenarios.
In reference to the results obtained from “5.3 Experiment Yields”, it was found that the percentage yield for all experiments (excluding the non-filtered one) were relatively impressive, but predictable. In practice, getting 100% yield is incredibly difficult if not essentially impossible. Often reactants or products can be lost to the environment, not all of the reactants could react or other factors could impede the reaction. Although in this experiment, a different factor was the cause of the loss of yield percentage. The manufacturers of aluminium cans use an aluminium alloy when making the cans, therefore causing the aluminium to have impurities. This was also noticeable when the reaction of the aluminium with the potassium hydroxide took place; the black residue which was produced was the sign of impurity. A procedure which could have helped prevent this error would have been to soak the aluminium in NaOH (sodium hydroxide) which would get rid of the oxide layer that the aluminium contains and any other impurities. Another possible solution to increasing the percentage yield would be to immediately put the beaker in water and ice, straight after adding the sulphuric acid to the solution; allowing it to chill thoroughly for about 15 minutes. Considering this solubility data, some product will not precipitate from the solution. Considering this table and graph (shown in Results), an improved result would be obtained by precipitation in ice water. This would cool the solution down much faster allowing the crystals to grow at a much greater reaction rate. Whereas when it isn’t iced, but filtered immediately, much of the alum saturated solution will fall through into the beaker losing some content. Furthermore, when the alum crystal was being handled (transport to filter paper from beaker, etc.) alum would have been eluded. The consequence of this would result in less alum.
7.0 Conclusion This experiment aimed to investigate the effect of the amount of scrap aluminium on the alum crystal, when potassium hydroxide and sulphuric acid were kept constant. Regarding the outcome of each trial, the results were supported by the theory stated in the hypothesis: It was hypothesized that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly, when potassium hydroxide and sulphuric acid are kept the same. It was found that the aluminium’s mass had a definite effect on the amount of alum produced. It can be concluded that when the potassium hydroxide is kept constant as well as the sulphuric acid, the outcome will be relatively similar and will adjust accordingly to the weight of the scrap aluminium.
The crucial errors which were encountered in this experiment, which had a vast impact on the percentage yield, was the impurity of the scrap aluminium, the imprecision of handling the alum, and the improper cleaning procedure which was undertaken with each of the scrap aluminium pieces.
The results obtained prove the hypothesis correct which stated that if the weight of the scrap aluminium is increased or decreased then the amount of the alum crystal will adjust accordingly.
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