of some Oxides of Mercury, 129 



tained nearly at the same degree : for if, as many chemists 

 are used to do, and as sometimes happened to M. Paysse, 

 the oxide be exposed to too sudden a heat at the moment 

 when it acquires its beautiful colour as well as its brilliancv, 

 it loses not onlv its crystalline appearance, but it assumes 

 also a disagreeable shade of reddish brown : if the heat were 

 carried further, it would even be partially or completely dc- 

 oxvgenated, and the mercury in this case would assume its 

 primitive form, as the author, on several occasions, had an 

 opportunity of observing. 



If the quantity of muriatic acid with which the nitric acid 

 may be mixed is too great, and if it rise to several hundredth 

 parts of the dose employed, the particular combination re- 

 suiting from its union with the oxide of mercury assumes 

 not the characters of a simple hvper-oxvgenated muriate, 

 as might at first be presumed, but that of a new compound, 

 which dissolves onlv in very small quantity in water, and 

 the latter must even be boiling ; which becomes sublimed 

 alone in close vessels, taking or rather retaining its parti- 

 cular colour ; which is brownish red, without an appearance 

 of crystallization ; and which M. Paysse considers as a mu- 

 riate of mercury with excess of oxide, according to the re- 

 sults it gave when subjected to some experiments. 



When this compound is found in too large proportion 

 in the oxide of mercury which has been prepared^ it always 

 opposes the formation of the crystallized red oxide, as he 

 several times remarked in his experiments. On the other 

 hand, if the proportion be small it may be neglected, and 

 it even insulates itself from the rest of the oxide in the vessel . 

 in wiiich it is prepared : it occupies a line, and forms a se- 

 parate stratum towards the upper part of the mercurial mass. 



What M. Paysse has here mentioned in regard to the 

 advantage there is in the preparation of the red oxide of 

 mercury by nitric acid — that an acid, as free as possible 

 from muriatic acid, should be employed — he had remarked 

 in the experiments which he niade every year in his course 

 of chemical lectures ; but not being able to form a very just 

 opinion as to the results of some trials made on a small 

 scale, and almost always uncertain, he was desirous, before 

 he developed it, ^o observe with attention what takes place 

 in the large operations performed in manufactories where 

 considerable masses are used at one time. Now that all his 

 doubts on this subject are removed, and since he knows the 

 phamoniena which take place when several hundreds of 

 krloorammes of mercurial oxide arc treated in one opera- 



Vol. 22. No. SG. July 180.5. I lion, 



