TRANSACTIONS OF THE SECTIONS. 71 
The formula of the dry salt is therefore 2NH*Cl, AsClO*. The loss of water by 
exposure over oil of vitriol amounted to 4-27 per cent.; one equivalent of water gives 
3°71 per cent, During the desiccation, a little chlorine is evolved and replaced by 
oxygen. ‘ 
I am still engaged in prosecuting the investigation of the compounds of chloro- 
arsenious acid with the metallic chlorides, and in endeavouring to form corresponding 
acids containing iodine and bromine. 
Observations on Dry Collodion Processes. By W. 8. Wann, F.C.S. 
On the Source of Ammonia in Volcanic Emanation. 
By R. Warineton, F.C.S. 
At the Meeting of the British Association at Liverpool, 1854, the author demon- 
strated the existence, in the lavas of Vulcano, of nitride of boron, which by the action 
of watery vapour is converted into boracic acid and ammonia. Adopting an analo~ 
gous reasoning, he considered that, in volcanic districts where hydrated silicic acid 
and ammonia were the ordinary products, a similar compound of silicon and nitrogen 
should be met with. On examining the Pelagonites from the Hecla district, the author 
finds that they always contain nitrogen in combination, as he believes, with silicon as 
a nitride of silicon, and that the source of ammonia in volcanic phenomena may be 
principally attributed to the action of aqueous vapour, at high temperatures, on this 
compound. 
On an Instrument for maintaining a Water-Bath at constant Temperatures. 
By Joun Warteruouse, F.RS. 
' The author exhibited to the Chemical Section an instrument which he calied a 
“ Thermostadt,” the object.of which he explained to be, to afford the means of keep- 
ing a water-bath at a uniform and unvarying temperature for an indefinite period. In 
the accompanying sketch, A B is a glass tube bent upon itself, 
and when filled with spirit or other expansible fluid, forming a 
thermometer of large dimensions: the two ends of this tube are 
cemented into the brass cap and plate C, the end A being her- 
metically closed, and B open; D is a stuffing-box (into which 
the open end of the tube is cemented), through which the tube E, 
open at both ends, passes, and which may be fixed in any required Dj) '|= 
position by the tightening screw collar F; to the upper end of "yy ip 
this tube is attached a flexible tube, which may be connected with | 
an ordinary gas-pipe; G is a small tube screwed into the side of 
the stuffing-box D, and communicating with the tube B or stem 
of the thermometer, and serves as an attachment for another flex- 
ible pipe which connects the apparatus with the burners which 
are-placed under the water-bath. A small quantity of mercury, 
M, is introduced to separate the spirit in A from the open stem 
of the thermometer B. ‘The operation of the instrument is as 
follows :—the whole being immersed to the plate C in the water- 
bath, the gas passes through E into the tube B, and thence 
through G to the burners; as the temperature rises, the spirit 
expands, and causes the mercury to rise in B until it finally 
closes the terminal aperture of the tube E, when the gas ceases 
to flow; to prevent, however, the total extinction of the flame, 
which would now take place, a small hole, N, is pierced with a 
needle through the side of the tube E at about an inch from the 
end, which allows a sufficiency of gas to pass to support a speck 
of flame not larger than a large pin’s head. In operation the 
flame soon acquires its appropriate dimensions to keep the bath < 
at a perfectly steady temperature, the exact amount of which is determined by sliding 
the tube E in its collar, and thus giving the mercury a greater or less range. 
At first a difficulty presented itself in procuring a burner of sufficiently small aper- 
