TRANSACTIONS OF THE SECTIONS. 61 
On the Preservation of Albuminized Collodion Plates. 
By W. Syxes Warp, F.C.S. 
Having made numerous experiments on the application of albuminized collodion 
according to Taupenot’s process, in comparison with collodion washed and covered 
with gelatine, according to the process published by Dr. Hill Norris and others, the 
author found the albuminized collodion process to give better results in all respects, 
excepting that of deteriorating by keeping. He also found that plates prepared by 
Taupenot’s process were affected by the wood of the dark slide, especially in some 
instances in which he employed unvarnished cedar wood. 
Tn the hope of combining the advantages of both processes, he poured on the plates 
prepared in accordance with Taupenot’s process, and whilst yet wet, various solutions 
of gelatine and metagelatine, and found that these had the desired effect of enabling 
him to keep the sensitized plates without deterioration at least four times as long as he 
could, under similar circumstances, keep the plates not so protected. 
The additional coating of metagelatine also gives a clearness, brilliancy, and trans- 
parency to the negative which is seldom obtained by the ordinary process. The coat- 
ing of metagelatine is applied after the sensitized plate has been carefully washed, and 
may be dried by heat, or in the ordinary manner. 
The following is the formula preferred :— 
Dry metagelatine . . . 
Lump sugar .... . 
Glacial acetic acid .. . 
LANES nt hot 9 br awage eh dae 
- « . 10 grains, 
BK maps ce- li ywnde 
- « ». 2minims. 
» « « I ounce, 
wv e © © 
On the Processes for the Detection of Fluorine. 
By Professor G. Witson, ID., F.RS.E., F.C.S. 
The author made an oral communication on M. Nicklés’ recent observations on the 
etching of glass as produced by the vapour of fuming sulphuric acid at a high tempe- 
rature, and disputed the validity of Nicklés’ conclusion, that his results prove the in- 
applicability of glass to the detection of fluorine in the form of hydrofluoric acid. He 
also drew attention to the impossibility of detecting minute traces of this acid, if 
quartz, as proposed by Nicklés, was substituted for glass as the material to be etched, 
and stated his intention of publishing at length his investigations on the relative suit- 
ability of glass and quartz for the detection of fluorine. 
On the Time required by Compounds for Decomposition. 
By Dr. T. Woops. 
The object of this paper was to prove that all compounds require a certain length 
of time in which, under similar circumstances, they can be decomposed; that this 
_ time is invariable in amount, definite and specific. It was first shown experimentally 
that different compounds require different ‘ times” in which to decompose. This was 
done by making a galvanic pair, one end of which was zinc in sulphuric acid, the other 
end, in a porous cell, platina in the compound to be decomposed. When the metals 
are joined externally, a galvanometer being included in the circuit, the needle shows 
the amount of electricity in circulation, and consequently the rapidity with which tke 
zinc is being dissolved, and therefore the “time” in which the decomposition of the 
compound is going on, 
By successively using different compounds, the time for the decomposition of each 
"was seen, and for the same compound always to be the same under like circumstances, 
It was also shown that the length of time each compound requires for decomposition 
was proportional to the amount of heat absorbed by the decomposition ; the more 
heat absorbed the longer it required to absorb it; so that the interesting fact was 
proved, that all compounds require the same length of time to absorb the same quan- 
tity of heat in decomposing. It was shown that the galvanometer in this arrange- 
ment acted the part of a thermometer of chemical action, as the needle varied exactly 
with the amount of heat absorbed in a given time. 
The paper urged the importance of attention being paid to thermo-chemistry, and 
claimed the precedence of all others on the subject it treated of, as the “‘ time” of action 
