ithout the aid of heat or solution in alcohol;
second, those that are solvents when dissolved in alcohol. These solvents
are those which also develop a solvent action when heated to their melting
point in combination with pyroxyline.

Mr W.D. Field groups the solvents of pyroxyline into classes thus: Two of
the monohydric alcohols; compound ethers of the fatty acids with
monohydric alcohols, aldehydes; simple and mixed ketones of the fatty acid
series. These four classes include the greater number of the solvents of
pyroxyline. Those not included are as follows:--Amyl-nitrate and nitrite,
methylene-di-methyl ether, ethidene-diethyl ether, amyl-chloracetate,
nitro-benzene and di-nitro-benzene, coumarin, camphor, glacial acetic
acid, and mono-, di-, and tri-acetin.

Richard Hale uses the following solvent:--Amyl-acetate, 4 volumes;
petroleum naphtha, 4 volumes; methyl-alcohol, 2 volumes; pyroxyline, 4 to
5 ounces to the gallon of solvent. Hale used petroleum naphtha to hasten
the drying qualities of the varnish, so that it would set on the article
to be varnished before it had a chance to run off. It is, however, the
non-hygroscopic character of the solvent that makes the varnish
successful. This formula is very largely used for the production of
pyroxyline varnish, which is used for varnishing pens, pencils, &c., also
brass-work and silver-ware.

The body known as oxy-cellulose[A] is formed by the action of nitric acid
upon cellulose when boiled with it. The quantity formed is about 30 per
cent. of cellulose acted upon. When washed free from acid, it gelatinises.
It is then soluble in dilute alkalies, and can be reprecipitated from
solution by alcohol, acids, or saline solutions. Messrs Cross and Bevan
assign to it the formula C_{18}H_{26}O_{16}. It dissolves in concentrated
sulphuric acid, and with nitric acid forms a nitro body of the formula
C_{18}H_{23}O_{16}3(NO_{2}), which is prepared as follows:--The gelatinous
oxy-cellulose is washed with strong nitric acid until free from water, and
is then diffused through a mixture of equal volumes of strong sulphuric
and nitric acids, in which it quickly dissolves. The solution, after
standing for about an hour, is poured in a fine stream into a large volume
of water, by which the "nitro" body is precipitated as a white flocculent
mass. The product, after drying at 110 deg. C., was found upon analysis to
contain 6.48 per cent. nitrogen.

[Footnote A: "On the Oxidation of C