ME. G. GOEE ON HYDEOELU OEIC ACID. 
181 
tapped persistently to remove any adhering bubbles of air ; the receiver C was then also 
similarly filled and tapped, and inverted over mercury in a large mercurial trough. 
5‘5 cubic inches (—90128 cubic centims.) of the prepared hydrogen which had lain many 
hours in the measuring-tube in contact with the phosphorus was now transferred to the 
platinum apparatus, and the tube A inclined and persistently tapped, so as to shake out of 
it as perfectly as possible all the mercury. A stick of dry phosphorus was again placed 
in the gas for one hour to remove any oxygen introduced by adhering air-bubbles, or 
by air lodging in the crevice at the junction of the two tubes. 
The apparatus and its contents were next removed from the mercurial 
trough by means of the glass vessel D, which was about 8 inches high 
(=20 -4 centims) and 2 inches (=5T centims.) in diameter, and were sup- 
ported within this vessel by mercury at such a height that the figure “ 5 - 5 Cl” 
of the graduation upon the platinum-receiver coincided in horizontal posi- 
tion with the mark — (shown at E, fig. 7) near the top of the outer vessel. 
Additional mercury was now poured into the outer vessel until it attained 
this same indicated level at the atmospheric temperature, and was there 
fore at the same level inside and outside the platinum-receiver. The tube 
A being supported horizontally, a wet rag was now laid upon it near the 
sealed junction and heat applied gently to the outer end by means of a 
spirit-lamp until a barely visible redness was attained, this being quite sufficient to melt 
the enclosed fluoride of silver. This degree of heat was maintained about one hour, 
and near the termination of the heating-process a much higher and variable temperature 
was applied for a short time, but not sufficiently high to melt the reduced silver. The 
mercury in the outer vessel was kept at the original level during the heating-process &c., 
by raising or lowering the platinum apparatus as occasion required. The whole appa- 
ratus was then placed in a suitable air-bath, and gradually heated to a uniform and con- 
stant temperature of about 212°Fahr. ( = 100° C.), a thermometer being placed in the 
vessel of mercury D, and another near it in the air-bath. The platinum apparatus was 
raised gradually as the gas expanded, to keep the mercury at the original level, and the 
volume of enclosed gas was noted at the various temperatures. 
In each instance, during the decomposition of the silver-salt by the hydrogen, 
after the first expansion (produced by the heat) a very large reduction of volume oc- 
curred; for instance, 3 0*0 cubic inches (=163-87 cub. centims.) were reduced to 6 - 5 
( = 106-5 cub. centims.); and on removing the lamp and allowing the whole apparatus 
to cool to 50 or 60° Fahr. (=10° to 15 0- 5 C.), a still further and very large contraction 
invariably occurred; for instance, 6'5 cubic inches (=106-5 cub. centims.) became 
3-0 cubic inches (=49-161 cub. centims.), even while under a rarefaction of 5 niches 
( = 12-75 centims.) height of mercury. Similar contractions [to very small volumes at 
the atmospheric temperature took place in all the experiments. These reductions of 
volume were in the earlier trials somewhat due to small quantities of air present, the 
oxygen of which formed water with some of the heated hydrogen and condensed a little 
mdccclxix. 2 c 
