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 in Dr Muehlhaeusen’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 deg.  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.