-cotton to act as a filter. This vessel is filled
with spent nitro-sulphuric acid obtained as a waste product from the
nitro-glycerine manufactory, and the solution of starch in nitric acid is
sprayed into it through an injector worked by compressed air, whereby the
nitro-starch is thrown down in the form of a fine-grained powdery
precipitate.

In order to precipitate 100 kilos. of the acid solution of starch, it is
necessary to employ 500 kilos. of spent nitro-sulphuric acid. As it is
precipitated the nitro-starch collects on the gun-cotton filter, and the
acid liquor is run off through a tap placed beneath the perforated double
bottom of the vessel, and of course below the filter pad. The precipitated
starch is further cleansed from acid by repeated washings and by pressure,
until all trace of acidity has been eliminated, and the substance exhibits
a neutral reaction. The next step is to treat the nitro-starch with a 5
per cent. solution of soda, in contact with which it is allowed to stand
for at least twenty-four hours. The product is then ground up until a sort
of "milk" or emulsion is obtained, and lastly treated with a solution of
aniline, so that when pressed into cake, it contains about 33 per cent. of
water, and 1 per cent. of aniline.

Dr Muehlhaeusen, working on these lines in the laboratory, prepared nitro-
starch which contained 10.96 and 11.09 per cent. of nitrogen. When in the
state of powder it is snow-white in colour; it becomes electrified when
rubbed; it is very stable, and soluble even in the cold in nitro-
glycerine. He has also prepared a tetra-nitro-starch containing 10.58 and
10.50 per cent. of nitrogen, by pouring water into a solution of starch in
nitric acid which had stood for several days. The substance thus produced
in the laboratory had all the properties of that prepared by the other
process.

The production of penta-nitro-starch is effected by adding 20 grms. of
rice-starch--previously dried at a temperature of 100 deg.C., in order to
eliminate all moisture--to a mixture of 100 grms. of nitric acid, specific
gravity 1.501, and 300 grms. of sulphuric acid, specific gravity 1.8 (some
tetra-nitro-starch is also formed at the same time). After standing in
contact with these mixed acids for one hour the starch has undergone a
change, and the mass may now be discharged into a large quantity of water,
and then washed, first with water, and finally with an aqueous solution of
soda. The yield