by this formula is
very insoluble in the compound ethers and other solvents of pyroxyline,
and is seemingly only converted or gelatinised by the action of the
solvent. The next formula produces a mixture of tetra-and penta-nitro-
celluloses hardly soluble in methyl-alcohol (free from acetone), but very
soluble in anhydrous compound ethers, ketones, and aldehydes:--

Nitric acid, sp. gr. 1.435 8 lbs.
Sulphuric acid, sp. gr. 1.83 15-3/4 lbs.
Cotton 14 oz.

Temperature of nitration, 60 deg. C. Time of immersion, forty-five minutes.

The 60 deg. of temperature is developed by mixing the acids together. The
cotton is allowed to remain in the acid until it feels "short" to the rod.

The following table, due to Mr W.D. Field, shows very plainly the great
variation in the time of the immersion and the temperature by seemingly
very slight causes. It extends over fourteen working days, during which
time it rained four days. The formula used is that given above, except
that the specific gravity of the nitric acid is somewhat lower. The
product obtained differs only from that produced by using nitric acid of
specific gravity 1.43 in being soluble in methyl-alcohol. From 30 to 35
lbs. of pyroxyline were produced in each of the fourteen days.

A careful examination of this table will prove very instructive. The
increase in yield varies from 31 per cent. to nothing, and the loss runs
as high as 10 per cent., yet care was taken to make the product uniform in
quality. On the days it rained there was a loss, with the exception of the
fourth day, when there was neither a loss nor a gain. On the days it was
partly clear, as just before or after rain, the table shows a loss in
product. We can explain this fact by reason of the moisture-absorbing
qualities of the cotton. On the rainy days it would absorb the moisture
from the air until, when immersed in the acids, they were weakened, and
the fibre dissolved more or less in weakened acid, producing what is known
as "burning" in the batch. It will also be noticed that on days which show
a loss, the time of the immersion was correspondingly short, as on the
a loss, the time of the immersion was correspondingly short, as on the
tenth, twelfth, and seventh days.

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