1 70 On the Atomic Weight of Oxalic Acid and of Mercwry. 



in the cold, repeated desiccation on a gentle sand heat, and 

 some hours boiling, the combination was incomplete in every 

 instance. 



Dr. Thomson states (First Principles, vol. ii. p. 404-) that 

 pernitrate of mercury, which he had accidentally formed, con- 

 sisted of Nitric acid 6*75 



Peroxide of mercury 27* 



which he makes one atom of each. But on the affusion of water 

 it was decomposed, peroxide remaining. The same happens 

 with the " super" sulphates and " super" nitrates produced by 

 heat; except that the residual salts are subsulphates and sub- 

 nitrates. Surely this decomposition indicates a deficiency, not 

 an excess of acid ; and it does not take place with the salts pro- 

 duced by double decomposition from corrosive sublimate. The 

 acetate which gave out some acid by heat in evaporation, de- 

 composed in water, like the "super" nitrate, &c. and required 

 a little additional acetic acid to complete the solution. That 

 which crystallized by spontaneous evaporation dissolved per- 

 fectly ; as do the sulphate, nitrate and muriate, with the same 

 equivalent of acid. In precipitating a metallic bicarbonate 

 in a nearly boiling solution, some effervescence would be ex- 

 pected ; yet none occurred in Experiment 4, though part of 

 the carbonate remained dissolved, and was subjected to the 

 heat of a boiling water-bath. It would also be a curious cir- 

 cumstance, if a metallic binoxalate should be so exactly pre- 

 cipitated, that the supernatant liquor would not affect litmus 

 paper, as in Experiment 5, more particularly where, as in that 

 case, evaporation, or heat, was necessary to induce any pi'eci- 

 pitation at all. The inference follows, that these are not bi- 

 salts ; nor the others with the same equivalent of acid. The 

 results of the 6th Experiment do not bear upon the question, 

 at least not favourably to my view of it ; but it seemed fair to 

 quote them. 



There is an objection to the inference above, that if the red be 

 a deutoxide of mercury, it should require two atoms of acid ; 

 an objection equally applicable to the salts of copper. But these 

 salts do not manifest the repugnance to crystallization which 

 usually characterizes the salts of such peroxides ; and I am 

 not acquainted with any metallic bicarbonate capable of sup- 

 porting the heat of boiling water. Cinnabar, the most inti- 

 mate combination of mercury with sulphur, and which there- 

 fore (without evidence to the contrary) should be regarded as 

 atom to atom, consists of Sulphur... 2* 

 Mercury... 12*5 



Thus giving the same number for mercury as inferred above, 



and 



