The stability of guncotton or its permanency during storage is tested by exposing it to an agreed temperature and noting its behavior. This is preferably done by the method devised by Abel, in which the ,guncotton is placed in a test tube which is partly immersed in the water contained in a water bath, the mouth of the test tube being closed by a cork stopper from which a piece of partly moistened test paper is suspended by means of a platinum wire. When the guncotton begins to decompose, it gives off nitrogen oxides, which are absorbed by the moisture on the test paper and re act with the reagents with which the paper is cov ered to produce a color, and as only the lower half of the paper is moistened, the color first appears as a brown line at the point of demarcation be tween the wet and dry parts of the paper. In making the test the water in the bath is heated up to time agreed-upon temperature, and main tained at that temperature by means of a tem perature-regulator. The test tube, filled and fitted as above described, is plunged into the water bath to the prescribed depth and a stopwatch started. A piece of paper upon whieh a line of the agreed depth of color has been drawn (known as the standard-tint paper) is placed beside the test tube, and the paper within the tube is carefully watched. In order that the guncotton shall pass the test, no colored line equal in depth to that on the standard tint paper must appear on the test paper within ten minutes when the gun cotton is exposed to a temperature of 73° C.
(170° F.). This test is known as the Abel heat test.
Aside from the use of cellulose nitrates for guncotton for military purposes, for which object the product is finely pulped and compressed and undergoes the highest nitration possible, it is also employed in various important industrial applications. The solubility of pyroxylin in ether alcohol, which was discovered by Dr. May nard, of Boston, in 1847 or 1848, afforded the liquid since known as collodion (q.v.), which can be used as a substitute for sticking plaster and as a vehicle for medicine. Subsequent applica tions of the cellulose nitrates have been the coat ing of photographic plates by collodion, the manu facture of celluloid (q.v.), the pyroxylin var nishes invented by Crane, and the making of artificial silk, artificial leather, and transparent films for photography.
From the returns of the last United States census it appeared that in 1900 there were ten establishments in three different States engaged in the manufacture and sale of cellulose nitrates, and that they employed $255,343 of capital and had 163 employees. There were produced 922,799 pounds of the various cellulose nitrates, having a value of $486,773, and there were consumed 691,115 pounds of cotton and 8,247,668 pounds of mixed acids. In addition there were pro duced and consumed in other establishments 2, 739,834 pounds of cellulose nitrates, making a total product for the year of 3,662,633 pounds of cellulose nitrates.