242 Mr. Donovan on the ; [Oct. 



In examining the number of the oxides of mercury, it was 

 necessary to have some standard analysis of the black and red 

 to compare with those contained in the salts. As from the great 

 difference of the foregoing statements, I could not determine 

 which to adopt ; and as there are circumstances in obtaining the 

 black oxide, which, not being hitherto known, were not attended 

 to, I thought it adviseable to go through the analysis of the black 

 and red oxides as a preliminary step. What these circumstances 

 are will appear from the following section. 



Sect. I. — Action of the pure Alkalies and Alkaline Earths on the 



Salts of Mercury . 



1 . With a view of obtaining black oxide of mercury, I treated 

 calomel in different ways, with solution of pure potash, such as 

 boiling, trituration, &c. and in this way obtained oxides differing 

 in the intensity of their shade. When a large quantity of calomel 

 was triturated with small quantities of solution of potash, until 

 further additions came off strongly alkaline, a powder of a dark 

 olive colour was obtained. 



2. When muriatic acid was digested on this powder, it became 

 greyish-white. When the liquid part was filtered off, and pot- 

 ash added to it, a bright yellow powder was precipitated. When 

 the greyish-white powder remaining on the filter was treated 

 with potash, it afforded a black powder. When this black 

 powder was digested with muriatic acid as before, the filtered 

 solution afforded no yellow precipitate with potash. 



3. Thus the oxide contained in calomel had been resolved into 

 a black and a yellow portion. From this, it appeared that this 

 oxide is intermediate between the black and the peroxide ; and 

 hence it would follow that calomel is a muriate of the deutoxide, 

 and that the true protomuriate would be the greyish-white 

 powder. Accordingly when this powder was sublimed, a large 

 quantity of metallic mercury was obtained along with a muriate 

 which afforded black and yellow oxide like calomel. But these 

 inferences are only apparently true, as will appear. 



4. These processes being repeated a number of times, the 

 same results were sometimes obtained, but often they were quite 

 different. At length it appeared that the manner of using the 

 alkali was the cause of the difference. When a very small 

 quantity of calomel (about 10 gr.) was well triturated with a little 

 water, and afterwards with a large quantity of alkaline solution, 

 poured on at one dash, an intensely black oxide was produced, 

 which, when digested with muriatic acid, afforded no yellow 

 oxide to it. When a small quantity of calomel was triturated 

 with successive small portions of alkaline solution, the oxide 

 separated was grey, and gave alittle yellow oxide to muriatic acid. 

 But when the quantity of calomel was great, and successive 

 portions of alkaline solution small, the resulting powder contained 

 a great quantity of yellow oxide mixed with black, and hence its 

 colour was olive green. In certain cases also, T found that by 



