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 in Dr Mühlhäusen's experiments was 147.5 per cent.

The substance thus formed is now heated with ether-alcohol, the ether is
distilled off, and the penta-nitro-starch appears as a precipitate, whilst
the tetra-nitro-starch, which is formed simultaneously, remains in
solution in the alcohol. As obtained by this process, it contained 12.76
and 12.98 per cent. nitrogen, whilst the soluble tetra-nitro-starch
contained 10.45 per cent.

Hexa-nitro-starch is the product chiefly formed when 40 grms. of dry
starch are treated with 400 grms. of nitric acid, specific gravity 1.501,
and allowed to stand in contact for twenty-four hours; 200 grms. of this
mixture are then poured into 600 c.c. of sulphuric acid of 66° B. The
result of this manipulation is a white precipitate, which contains
13.52-13.23 and 13.22 per cent. nitrogen; and consists, therefore, of a
mixture of penta- and hexa-nitro-starch.

The experiments undertaken with these substances demonstrated that those
prepared by precipitating the nitro-starch with strong sulphuric acid were
less stable in character or properties than those which were precipitated
by water or weak sulphuric acid. Dr Mühlhäusen is of opinion that possibly
in the former case a sulpho-group may be formed, which in small quantity
may occasion this instability.

The following table shows the behaviour of these substances prepared in
different ways and under various conditions:--