Acetate of Soda. 283 



Sulphate of manganese has only lately been employed by 

 manufacturers for obtaining bistre. If to a solution of 

 sulphate of manganese we acid caustic ley, a brownish 

 white precipitate falls, which, by exposure to the air, be- 

 comes dark brown. This precipitate constitutes bistre. 

 To fix it on the cotton, the latter is dipped in a solution of 

 sulphate of manganese, dried and passed through strong 

 caustic ley. At first the cotton acquires but little colour. 

 After some time it becomes dark brown.* 



Acetate of 'lead.— -Good sugar of lead should be completely 

 white, afford an acid re-action and give a red colour to blue 

 litmus paper. 



Sugar of lead consists of acetic acid and oxide of lead. 

 It decomposes all sulphuric acid salts, and changes them 

 into acetates. If solutions of sugar of lead and alum be 

 mixed together, a white preciptitate falls. This is sul- 

 phate of lead produced from the sulphuric acid of the alum 

 and the lead of the sugar of lead. The acetic acid of the 

 sugar of lead remains in the supernatant liquor in combi- 

 nation with the alumina of the alum, and forms a solution 

 of acetate of alumina. 



Solutions of iron and copper vitriol, when mixed with a 

 solution of sugar of lead, give the same precipitate of sul- 

 phate of lead, as both are sulphuric acid salts. 



In the former case, the supernatant liquor contains 

 acetate of iron, in the latter, acetate of copper in solution. 



In this way, by means of sugar of lead, all soluble sul- 

 phuric acid salts may be converted into acetates. 



As sugar of lead is easily soluble, it may be agitated with 

 the solutions of the sulphates, so as to decompose them by 

 stirring them sufficiently long. 



Acetate of lead produces no injurious effect upon calico. 

 In situations where animal substances putrify, for ex- 

 ample, near emunctories, stables and dunghills, this salt is 

 covered with a blackish gray coating. This proceeds from 

 sulphur contained in the putrifying bodies which forms 

 sulphuret of lead. Calico impregnated with sugar of lead 

 mordant must be kept away from such situations. 



Acetate of soda decomposes sulphuric acid salts like sugar 

 of lead, but with a less favourable result, for the soda 



• For specimen of Manganese Bronze, see Records, i. 17.— Ecu. 



