96 On the aériform Compounds 
with the mixture, and covered by opake cases. When the stop- 
pers were removed under water, at various intervals after the mix- 
ture, from a few minutes to 39 days, no diminution whatever of 
volume was found to have taken place; and after having removed 
the chlorine by liquid potash, the carburetted hydrogen gas gave 
the usual products of carbonic acid, and consumed the usual pro- 
portion of oxygen. Mixtures also of hydrogen and chlorine, and 
of carburetted hydrogen and chlorine, standing over water in 
graduated tubes, which were shaded by opake covers, sustained 
no loss of bulk, except what arose from the absorption of chlorine 
by the water, the combustible gas remaining wholly unaltered. 
It may be considered, therefore, as quite essential to the mutual 
agency of these gases, that they should be subjected to the in- 
fluence of light. But it is not necessary that the direct rays of 
the sun should fall on the mixture, the light of a dull and cloudy 
day being fully adequate to the effect. On a day of this sort, I 
filled several stoppered vials, graduated into hundredths of a cu- 
bic inch, with a mixture of 30 volumes of carburetted hydrogen 
with from 80 to 90 of chlorine, and uncovering them all at the same 
moment, exposed them to the feeble light which was then abroad. — 
By exposure of one of the vials during half a minute, no diminu- 
tion of volume was found to have been effected; another vial, 
opened under water when one minute had’ elapsed, showed an 
absorption of five parts; a third in two minutes had lost fifteen 
parts; a fourth in four minutes 25 parte; and a fifth, opened in 
five minutes, contained only 50 volumes out of the original 110. 
The products, resulting from the contact of carburetted hydro- 
gen and chlorine, under circumstances favourable to their mutual 
action, have been described by Mr. Cruickshank, with whose ex- 
perience on this point my own entirely agrees. When rather 
more than four volumes of chlorine are kept in mixture with one 
volume of gas from stagnant water, the products are muriatic 
acid gas, and a volume of carbunic acid equivalent to that of the 
pure carburetted hydrogen; and this, whether the mixture be 
exposed to direct or indirect solar light ; the only difference be- 
ing that the less intense the light, the more slowty is the effect 
produced. When less than four volumes of chlorine are em- 
ployed, the residue consists of muriatic and carbonic acids, car- 
bonic oxide, and undecomposed carburetted hydrogen, the pro- 
portions of the two last increasing as, within certain limits, we 
reduce the relative quantity of chlorine. ‘These changes were 
ascertained, both by Dr. Davy and the late Dr. Murray, to de- 
pend cn the presence of moisture, which is unavoidably introduced 
in the common mode of operating; for when the gases, first 
perfectly dried, were mixed in an exhausted glass vessel, and ex- 
posed even to the direct rays of the sun, no mutual action was 
found 
