on the Action of Water and Air on Lead. 91 



and with sulphuretted hydrogen a decided brown, but not 

 equal in tint to that produced by distilled water which had 

 been three or four days in contact with lead. 



Some of the same carbonate was put into a phial with the 

 solution of carbonic acid and another portion of the carbonate 

 into another phial with distilled water. When the liquids were 

 tested after standing two days, the carbonic acid solution gave 

 a brown colour, the distilled water a very pale tint. 



33. To ascertain the degree of solubility of carbonate of 

 lead in the solution of carbonic acid, a solution of carbonate 

 of lead was formed by putting a quantity of carbonate of lead, 

 obtained as before stated, into the solution of carbonic acid in 

 distilled water. After standing some days the clear liquid was 

 drawn off for experiment (a). 



Another solution was obtained by washing some good ce- 

 ruse on a filter, until the filtered liquid, when tested by sul- 

 phuretted hydrogen, gave no further diminution of tint. By 

 continued effusions of distilled water, the solution of carbonic 

 acid was then filtered through the washed carbonate, and the 

 liquid preserved for use (|3). 



34. A standard solution of lead was then made by dis- 

 solving one grain of pure oxide of lead in acetic acid, and eva- 

 porating this to dryness at the heat of boiling water, and dis- 

 solving the resulting acetate in 1000 grains of distilled water. 



35. When a portion of the standard solution was diluted 

 with about 83 parts of distilled water, the tint produced on 

 testing this by sulphuretted hydrogen and the solution in car- 

 bonic acid (a), was equal. When the standard solution was 

 diluted with between 50 and 60 parts of distilled water, the 

 tint produced on testing it and the solution (0) was equal. 



36. Thus it appears that such a solution of carbonic acid as 

 I used is capable of holding in solution about from so ^ th 

 to ^-g-i—gth of oxide of lead if presented to it in the state 

 of carbonate. These solutions immediately become turbid 

 when carbonate or bicarbonate of potash is added; but, with 

 (a) at least, no effect was produced by the action of any of 

 the other tests tried on the distilled water, nor is it made 

 turbid by agitation. 



37. When clean cuttings of lead were immersed in solutions 

 of common salt, and sulphate of lime, in the proportions of one 

 part salt to one thousand parts distilled water ; in one ounce 

 of water with a drop of sulphuric acid ; in the spring water 

 (par. 5.) boiled, and the liquids tested after three weeks, no in- 

 dication of their holding lead in solution could be perceived. 



But the power of saline bodies to prevent the action of 

 pure water on lead is a part of the subject which, noticed 



N 2 



