1814.] On the Oxides of Arsenic. 175 



muriatic acid united with black oxide of mercury, and an oxide of 

 arsenic containing less oxygen than arsenious acid. It seems to 

 have been a mixture of calomel and chloride of arsenic. 



Such are the new experiments of Berzelius, by which he con- 

 siders himself as warranted'to set aside the conclusions drawn from 

 lits own former experiments, and from those of Proust, Rose, 

 Bucholz, and Thenard, which all correspond very well with each 

 other. But I do not consider these new experiments, however 

 carefully they may have been made, as capable of refuting the 

 former experiments on the composition of arsenic acid. These 

 experiments are in themselves extremely easy and simple, and one 

 cannot see any source of ambiguity or fallacy that would account 

 for so great an error as that of nearly 15 per cent, in the weighing, 

 which must be supposed if Berzelius' new determination be ad- 

 mitted as correct. To be able to judge with some precision of the 

 nature of this experiment, I repeated it myself in the following 

 manner: — I put 100 grains of metallic arsenic into a retort, and 

 converted it into arsenic acid by means of nitric acid. I then dis- 

 tilled off the nitric acid, and exposed the dry arsenic acid in the 

 bottom of the retort to the greatest heat which I could raise by 

 means of an Argand's lamp; and this heat was continued till the 

 retort became perfectly dry. The retort was then weighed. It was 

 found that the weight of the arsenic had increased from 100 grains 

 to 152-4 grains. Now in this experiment, which 1 presume is 

 similar to what had been previously done by Proust, Rose, Bucholz, 

 and Thenard, I do not perceive any source of fallacy. The arsenic 

 was merely dissolved in the acid, and the acid distilled off' into a 

 receiver ; and, for greater security, what came over into the receiver 

 was examined, but no traces of arsenic acid, or of arsenic in any 

 state, could be found in it. No arsenic therefore was lost ; nor 

 can any source of loss be pointed out; no filler was employed ; 

 nothing, in short, which could account for the !o«s of Ingrains, 

 the quantity wanting to make up the weight of the arsenic acid, 

 according to the conclusion of Berzelius; nor can it be said that 

 the arsenic was not wholly converted into arsenic acid; for 1 dissolved 

 it in water, and found a residue of white oxide of arsenic weighing 

 exactly 0-5 grain. Now this small deficit, which does not exceed 

 0*06 grain of oxygen, I added to the weight of the arsenic acid 

 found ; for the weight of the acid as I first took it was only 15234 

 grains. 



It is by no means unlikely that the heat of an Argand's lamp was 

 Dot sufficient to free the arsenic acid from the whole of its water ; 

 but if we suppose that any water adhered to it, this makes still 

 farther against ;hc conclusion of Berzelius; for in that ease the 

 true iu weight was less than I found it. As then-fore the 



eriments made by myself and others to convert arsenic into 

 arsenic acid Bre exceedingly simple and easy, and as they are quite 

 inconsistent with the new determination of Berzelius, I do not see 

 any other alternative at present than to conclude that this ingenious 



