366 Fiirthtr analytical Experiments relative id 



B. Forty grains of this salt were dissolved in water and de» 

 compo-^ed by hydro-sulphuret of potash: the products of this 

 deco'.nposilion were prunsiate of potasli and black siilphuret of 

 mercurr; the quantity of the former coidd not be ascertained 

 with accuracy, owing to the escape of much of the prussic acid, 

 but that of the sulphuret amounted to 37'2 grains. 



C. Disappointed in my attempt to estimate the quantity of 

 prussic acid by the last experiment, owing to its very volatile 

 nature, I availed myself of the property I had discovered in the 

 hvdrogurctted sulphnrets, of converting the prUssic acid at the 

 moment they detach it from prussiate of mercurv, into sulphu- 

 retted chyazic acid ; whicli being much less volatile, and having 

 a stronger attraction for alkaline bases than the prussic, could 

 not esca])e from the liquid, and would give me the (|uantity of 

 prussic acid it represented, by deducting from its weight that 

 of the sulphur which I knew to exist in it. I therefore dissolved 

 ten grains of prussiate of mercury in hot water, and poured hy- 

 droguretted sulphuret of soda into the solution until it no longer 

 occasioned a black precij)itate. This black precipitate when 

 dry weighed 9'3 grains : to the liquid from which it was sepa- 

 rated I added a few drops of diluted sulphuric acid : these 

 caused a separation of a minute quantity of sulphur, which warj 

 got rid of by subsidence, after which I poured into it an aqueous 

 solution of the two sulphates of copper, and of black oxide of iron, 

 in which the former salt was to the latter by weight as 2 is to 3j 

 until no further effect was produced. By these means I threw 

 down the whole of the sulphuretted chvazic acid contained in 

 the liquid, and collected it combined with protoxide of copper 

 in the form of an insoluble white salt, which weighed 9'7 grains. 



But as 100 grains of this salt contain 40'G2 grains of sul- , 

 phuretted chyazic acid, composed of 26'3J) sulphur and 14-23 

 prussic acid, according to my analysis, Phil. Trans, for 1S14, 

 page ^49, Exp. C. (corrected by calculations in the table facing 

 page 370 of the present paper), therefore the before-mentioned 

 9*7 grains represent 1*38 of prussic acid, which according, to 

 this experiment is the quantity existing in 10 grains of prussiate 

 of mercury. 



D. I had next to ascertain how much red oxide of mercurv 

 was represented by the 37" 2 grains of black sulphuret obtained 

 in Experiment B, and by the 9 3 grains of the same substance 

 obtained in Experiment C. In order to effect this, I made tlie 

 following experiment: 25 grains of corrosive sublimate were 

 dissolved in wat.'r, and decomposed by hydro-sulj)h\iret of pot- 

 ash ; the black sulphuret thus formed weighed 21 "5 grains, which 

 therefore represents 19*C4 grains of red oxide of mercury, that 



being 



