556 
DR. A. SCOTT ON THE COMPOSITION OF WATER BT VOLUME. 
In o]’der to analyse the residue it was passed into the jar H, and a quantity of 
oxygen drawn from the oxygen apparatus and measured in B, in exactly the same 
way as the residue ; then both were mixed and again measured, giving the corrected 
volume ]4’8 for the volume before explosion. After explosion 5'9 remained, and 
on treatment as in the other experiment described above, first with potassium hydrate 
and then with pyrogallol, no carbon dioxide could be detected, and all the gas was 
absorbed with the exception of a minute bubble of as nearly as possible 1 millim. in 
diameter. The residue of 5‘98 was therefore pure hydrogen, being confirmed by the 
analysis f (14’8 ~ 5'9) = 5’93. 
The coml3inincr volumes are therefore— 
6808‘5 — 6‘0 = 6802‘5 of hydrogen with 3395‘8 of oxygen, 
or— 
2-0028 „ „ 1-0 
In order to determine the degree of accuracy with which the volumes of the gases 
might be determined, the same volume of gas was repeatedly measured during a 
fortnight, so as to have it under much greater variations of temperature and pressure 
than ever occurred during any experiment. The following corrected values were 
found :— 
3279- 4 
3280- 3 
3280-6 
3280-1 
3279-7 
3279-4 
3279-8 
giving as a mean 3279-9, with the probable error on a single observation of fi: -3. 
These are highly satisfactory when one remembers that ‘I millim. in pressure 
corresponds to about *5 in volume, and "01° C. to rather more than -I. 
In the followdng experiments the volumes of the gases measured and the residues 
are given reduced to 0° C. and 760 millims. pressure. They are divided into two 
j^rimary series, corresponding to the two forms of measuring vessel employed; and 
these are again divided into sub-series, according to the sources of the oxygen and 
hydrogen. 
All experiments are given which were completed, except a very few, which were 
contaminated by such large quantities of impurity, such as carbon dioxide (as in the 
first experiments with oxygen from mercuric and argentic oxide), wdiich rendered the 
determination of the ratio impossible or very unsatisfactory. The first seven experi¬ 
ments of Series Ia were also omitted, as they were rendered practically valueless, as 
w^ere all those formerly published, owdng to the use of vaseline as a lubricant for the 
glass taps. Experiments VIII. and IX. show ho-w this source of error was detected, 
and on using syrupy phosphoric acid as the lul)ricant, and safety taps with cups, 
