SCIENTIFIC SUMMARY. 
253 
atmospheric air was reduced to ^-i^thof its volume ; oxygen gas to -s-^th of its 
volume ; hydrogen to T ^rth ; and nitric oxide to -^th. None of the gases 
exhibited any appearance of liquefaction, even in these high states of con- 
densation, notwithstanding that their densities must have been but little 
inferior to that of water. 
Professor Graham, in continuing his researches upon the diffusion of liquids, 
has discovered a new means of separating substances which have, with diffi- 
culty, yielded to the ordinary processes of chemical analysis. By allowing 
complex organic and inorganic liquids to diffuse through a parchment-paper 
diaphragm, he finds that they separate into two classes, which he terms 
crystalloids and colloids, the process of separation being called dialysis. By 
the dialytic method of analysis, arsenic has been removed from a complicated 
organic solution, soluble silicic acid for stone-preservation has been separated 
from the accompanying salts, and many other equally important but hitherto 
difficult separations have been with ease effected. 
Some remarkable experiments have been performed by Dufour on the 
alteration in the freezing and boiling points of liquids. By preparing a liquid 
of the same specific gravity as water, but immiscible with it, small globules of 
water would remain floating about with perfect freedom of motion in the 
centre of the mixture. The medium employed by Dufour was essence of 
cloves, to which a few drops of oil had been added. By then carefully applying 
heat to this liquid, a temperature far above the boiling point could be 
attained without causing the ebullition of the globules of water ; small spheres 
of water, of half an inch or more in diameter, being readily brought to a tem- 
perature of 300° Fahrenheit without alteration, whilst smaller spheres could 
frequently be heated to a temperature of 350° without entering into ebulli- 
tion, although at this temperature steam has a tension of eight atmospheres. 
At these high temperatures the globules were as calm and limpid as at the 
ordinary temperature ; but when carried against the side of the vessel, or 
touched with any solid body, an explosive formation of steam was the result. 
Similar phenomena were produced with other liquids, such as chloroform, &c. 
In a like way it was found that the freezing point of water could be 
retarded. 
By cooling the medium in which the aqueous globules were floating in 
equilibrium, the water could be reduced to twenty or thirty degrees below 
the freezing point without solidifying. Ultimately they became suddenly 
converted into solid lumps of ice ; and this change could always be effected 
in them by contact with solid bodies. As in the former experiments, this 
persistence of the liquid condition under severe cold is not confined to water : 
sulphur, phosphorus, and naphthaline, all present similar phenomena ; and 
were it not for the difficulty in finding suitable media, it is likely that many 
other substances would be affected in the same way. It is likely that these 
researches will throw considerable light on the formation of hailstones, and 
many minerals which show traces of igneous fusion. 
II. Applied Chemistry. — Gorup-Besamez informs us that ozone, when 
properly employed, is a most effective agent for restoring books or prints 
which have become brown by age. 
His process is to place a bit of phosphorus in a wide-necked glass carboy, 
