1824.] Fulminate of Silver. 415 



When fulminate of silver is put into a solution of potash, oxide 

 of silver is separated, and fulminate of potash is formed ; but 

 the decomposition is very incomplete ;. oxide of silver continues 

 to precipitate during the evaporation of the fluid, even at the 

 expiration of some days ; the results obtained are very variable, 

 depending upon the quantity of potash, and unquestionably also 

 upon the formation of double compounds. 



One hundred parts of fulminate of silver produced 27*14; 

 2969 and 3 1*45 of oxide of silver. Being unable to employ 

 this method of analysis to determine the quantity of base com- 

 bined with the fulminic acid, we had recourse to chloride of 

 potassium ; it does not indeed decompose the fulminic acid ; it 

 precipitates the oxide of silver combined with it in the state of 

 chloride, and produces fulminate of potash ; 2*252 parts of fulmi- 

 nate of silver thus decomposed by chloride of potassium slightly 

 in excess, yielded 1*202 of chloride of silver; estimating this 

 quantity of chloride in the state of oxide, 100 of fulminate con- 

 tain 38*106 of oxide of silver as a base. 



The fulminate of potash obtained in this experiment, decom 

 posed by muriatic acid, yielded 1*210 of chloride of silver; or 

 100 of fulminate contain 38*359 of oxide of silver regarded as a 

 constituent of the fulminic acid. These two quantities of oxide 

 of silver differ so little from each other that we may conclude 

 the fulminate of silver to contain twice as much oxide as is requir- 

 ed to saturate the fulminic acid. The total of these two quanti- 

 ties of oxide amounts only to 76*464, instead of 77*528, which 

 ought to have been obtained; but the conclusion which we have 

 drawn from our experiment is not on this account much less 

 accurate.* 



Knowing the quantity of oxide contained in the fulminate of 

 silver, we endeavoured to determine its other elements, among 

 which are, as we already know, carbon and azote. We decom- 

 posed the fulminate of silver by oxide of copper; but as it was 

 verv requisite to dry the matters upon which we had to operate 

 perfectly, we shall begin by describing the process by means of 

 which we believe that we succeeded in effecting it; especially as 

 it is applicable to the analysis of any vegetable or animal sub- 

 stance. 



After having mixed the fulminate of silver with the oxide of 

 copper, and introduced the mixture into a moderately thick glass 

 tube, the external diameter of which was about one-third of an 

 inch, and its length nearly twelve inches, a, fig. 1 (PI. XXVIII), 

 it was connected with a tube b, containing chloride of calcium, 



• The alkaline chlorides ponies* the property of dissolving a small quantity of chlo- 

 ride of silver : this source of error we avoided in the following manner: we began by 

 evaporation nearly to dryness, and poured some nitric acid upon the residuum : by 

 heat, the chloride of potassium was quickly converted into nitrate, while the chloride 

 of silver suffered no change. 



