208 Mr. R. Phillips's Analysis of some Salts of Mercury. 



with but little success ; it is indeed true, that Berzelius {Essai 

 sur la Theorie des Proportio7is Chimiqiies, table, p. 21.) states, 

 that what he calls carbonas hydrargyrosus, consists of 9'4'7 car- 

 bonic acid +90*53 protoxide of mercury, or an atom of each; 

 but this, I take it for granted, is merely theoretical composi- 

 tion. 



Berthollet(Mt7«o/r£'s d'Arcucil, torn. iii. p. 89.) after men- 

 tioning the precipitation of pernitrate of mercury, by carbo- 

 nate of soda, to which I shall again advert: says, " On a fait 

 la menie experience avec une dissolution nitrique de prot- 

 oxide de mercure. Le precipite etait d'un jaune clair; il 

 a fait, apres avoir ete bien lave, une vive effervescence avec 

 I'acide nitrique. Lorsqu'on pousse fort loin les lotions, il prend 

 une couleur noiratre; et meme sa surface se noircit lorsqu' 

 on le laisse sous I'eau;" and he afterwards adds, " le prot- 

 oxide se combine avec lui, [I'acide carbonique,] et pent former 

 un carbonate, lequel cependant peut etre decompose par la 

 senle action de I'eau qui lui enlcve I'acide carbonique, quoique 

 difficilement." 



Upon considering these statements, I apprehend that Berthol- 

 let took the yellow precipitate for a carbonate, and the black 

 one for protoxide of mercury derived from its decomposition. 



To procure protocarbonate of mercury, I mixed a solution of 

 carbonate of potash with one of protonitrate of mercury ; the 

 precipitate at first produced was of a yellowish colour, and it 

 remained so until excess of the alkaline carbonate was added; 

 it then became immediately of a dark colour, and eventually 

 as black as the precipitate formed by caustic potash : I have 

 thei-efore no doubt that the yellowish precipitate, first ob- 

 tained, was a subprotonitrate, and it dissolved in nitric acid 

 without effervescence; if the solution of the nitrate be added 

 to an excess of that of the carbonate, the precipitate is at 

 once black. 



Two hundred grains of the precipitate procured with excess 

 of carbonate of potash, and dried by exposure to the air, were 

 dissolved in a weighed vial of dilute nitric acid; the loss of 

 weight was only 0*5 of a grain, and was evidently one of mani- 

 pulation merely ; this experiment I have repeated with similar 

 results. 



Under these circumstances, I am of opinion that a white 

 or yellow protocarbonate of mercury cannot be formed ; that 

 when the protocarbonate is precipitated it is of a black colour, 

 but loses its carbonic acid by drying in the air. 



BerthoUet states that percarbonate of mercury cannot be 

 formed ; he says indeed, correctly, that when bipermuriate of 

 mercury is treated with carbonate of potash, it is not obtained ; 



but 



