ae eee TS 
288 BUNSEN ON THE CACODYL SERIES. 
On repeating this experiment, 0°5504 grm. yielded 0°7911 
grm. sulphuret of arsenic; of which 0°7448 grm. produced by 
oxidation 0°2233 grm. of sulphur, and 1:342 grm. sulphate of 
barytes. The first experiment is equivalent to 66°12 per cent., 
the last to 65°38 per cent., which corresponds very closely with 
the theory. The whole results are, therefore, 
Calculated. ite IL. 
C, SOs 74 21°52 21°76 21°65 
H, yey 74°88 27 5°27 5°34 
ests O08 66°17 66°12 65°38 
QO ©. . 10000 7°04 6°85 7°63 
1420°70 100°00 100°00 = 100°00 
I have determined the specific gravity of the vapour of al- 
carsin again, because that given in my previous memoir agrees 
more with my former supposition than with the above compusi- 
tion. In order to avoid any error arising from the oxidation of 
the alcarsin, I prepared a new quantity expressly for this experi- 
ment, and boiled the mercury in the measuring receiver before- 
hand, so that the liquid collected on the top of the mercury, 
after the experiment was concluded, was quite free from any 
air. 
Liquid in the small glass tube . . . 0°2414 grm. 
Volume of the vapour . .. . . . 47°04C.C. 
Temperature of the oil-bath . . . . 148°5 centig. 
Higher level of the mercury in receiver 74 lines. 
Pressure of the oilcolumn . . . . 148 eu 
Barometer . . . se 335°5 aoe 
From these data the sanainte pe af the alcarsin is 7°555 ; 
and that calculated, is 
A vole::Carbor. 2) C4e 2 Pe SSG eS 
12.) ydrosens et es ee Nis 8256 
Pou Arsenie. 0803 Wer os 410 S654 
vol. (Oxygen?) 1). aterm PLO8G 
15°6649 : 2 = 7°8324. 
When we remember that in estimating the specific gravity of 
vapours by the method of Gay-Lussac the result must be too 
low, the difference above between that calculated and observed 
will appear small. I must confess, however, that the difference 
did at first appear to myself inexplicable, as I had used every 
