Chemical Experiments on Mercunj. 57 



have obtained, as we shall show hereafter. This los? of 

 0'7 is to be attributed ia part to what was dissolved by the 

 phosphoric acid which was formed, but still more, in our 

 opinion, to the potash. Mercuriid salts decomposed by 

 means of this alkali always retain some of it. M. Berthol 

 let has shown, that during the decomposition of these salts 

 by potash, ncidier the redundance of the latter, uor ebulli" 

 ' tiou, can entirely clear the solution of mercury. 



2. Of the Gray Oxide of Mcrcunj. 

 With phosphoric acid we treated ten graunries of gray 

 oxide, obtained by decomposing by ammonia a solution of 

 a sulphate of mercury at the nnninuiiri, strongly boiling the 

 precipitate to dissolve and separate all the triple salt that 

 might have united with it. From these 10 grammes we 

 obtained 9-2.5 of reduced mercury, and we concluded that 

 this oxide contains 7^ per cent, of oxygen. The mean 

 which we employed for obtaining the gray oxide of mer- 

 cury seems to us preferable to that of precipitation by 

 caustic fixed alkalies, which combine in part with th« 

 oxide precipitated, from which it is impossible entirely to 

 separate them. When, in the method wjth ammonia, some 

 portion of this adheres still to the oxide, v.'e may easily ex- 

 pel it by a moderate heat. 



3. Of the Act tun of the Phosphorous Acid upon the Salts 

 (f Mercury. 



Having, without success, attempted to analysethemercu- 

 rial salts by means of caustic potash, we determined to treat 

 them in a direct manner with phosphorous acid, and wc 

 obtained the following results; 



1. Phosphorous acid in excess decomposes all the mer- 

 curial salts, without exception, reducing their oxides into 

 running mercury, and entirely separating their radicals. 



2. When these salts are at the maxiumm of oxygenation, 

 it causes them to pass into the minimum before it dccom- 

 ])0ses them. 



3. Mercury is completely reduced t(^ the metallic state 

 by this means ; for, the oxide of mercurv being united to a 

 radical, w hich does not (juit it entirely until it arrive? at 

 the metallic state, the pliosphoric acid formed in the ope- 

 ration cannot dissolve the mercurial oxide, not beinsi i'l 

 contact with the mercurv untd it arrives at the metallic 

 state. The acids, before united to the oxides of mercurv, 

 cannot rcdissf)lve it while the pho^^phorous acid which de- 

 stroys the action is present. .Should u phosphate acci- 

 dent dly 



