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. 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 Muehlhaeusen 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:-- __________________________________________________________________ | | | | | SAMPLES. | | |____________________________________________| | | | | | | | | | A. | B. | C. | D. | E. | | Ignition-point |175 deg. C. |170 deg. C. |152 deg. C. |121 deg. C. |155 deg. C. | | Stability |Stable |Stable |Unstable|Unstable|Unstable| | Per cent. of N. | 11.02 | 10.54 | 12.87 | 12.59 | 13.52 | | 96 per cent. alcohol| Sol. | Sol. | Insol. | Insol. | Insol. | | Ether | Insol. | Insol. | Insol. | Insol. | Insol. | | Ether-alcohol | Sol. | Sol. | Sol. | Sol. | Sol. | | Acetic Ether | Sol. | Sol. | Sol. | Sol. | Sol. | |_____________________|________|________|________|________|________| These samples were prepared as follows:-- A. From 1 part nitric acid and 2 parts sulphuric acid (containing 70 per cent. H_{2}O). B. From 1 part nitric acid and water. C. From 1 part nitric and 3 parts H_{2}SO_{4} (con.). D. From 1 part nitric and 3.5 parts con. H_{2}SO_{4}. E. From 1 part nitric and 3 parts con. H_{2}SO_{4}.