Dangers in connection with the Manufacture of Guncotton, &c.—­Of all the nitro compounds, the least dangerous to manufacture are gun-cotton and collodion-cotton.  The fact that the Stowmarket Factory is within five minutes’ walk of the town shows how safe the manufacture of this explosive is regarded.  With the exception of the nitration and the compression into blocks or discs, the whole process is worked with a large excess of water, and the probability of an explosion is thus reduced to a minimum.  Among the precautions that should, however, be taken, are—­first, the careful extraction of the resinous and soluble substances from the cotton before nitration, as it was shown many years ago by Sir F.A.  Abel that the instability of the gun-cotton first manufactured in England and Austria was chiefly due to these compounds.  They are generally removed by boiling the cotton in a soda solution.

The actual nitration of cotton is not a dangerous operation, but the operations of wringing in the hydro-extractors, and washing the nitro-cotton after it leaves the first centrifugal machine, are somewhat so.  Great care should be taken that the wrung-out nitro-cotton at once comes in contact with a large excess of water, i.e., is at once immersed entirely in the water, since at this stage it is especially liable to decomposition, which, once started, is very difficult to stop.  The warmer the mixture and the less water it contains, the more liable it is to decomposition; hence it is that on warm and damp days the centrifugal machines are most likely to fire.  The commencement of decomposition may be at once detected by the evolution of red fumes.  Directly the gun-cotton is immersed in the large quantity of water in the beater and poacher it is safe.

In order that the final product may be stable and have good keeping qualities, it is necessary that it should be washed completely free from acid.  The treatment in the beater and poacher, by causing the material to assume the state of a fine pulp, in contact with a large quantity of water, does a good deal to get rid of the free acid, but the boiling process is absolutely necessary.  It has been proposed to neutralise the free acid with a dilute solution of ammonia; and Dr C.O.  Weber has published some experiments bearing upon this treatment.  He found that after treatment with ammonia, pyroxyline assumed a slightly yellowish tinge, which was a sure sign of alkalinity.  It was then removed from the water, and roughly dried between folds of filter paper, and afterwards dried in an oven at 70 deg.  C. After three hours, however, an explosion took place, which entirely destroyed the strong copper oven in which the nitro-cotton (about one oz.) had been drying.  The explosion was in some respects remarkable.  The pyroxyline was the di-nitro-cellulose (or possibly the penta-nitro?), and the temperature was below the igniting point of this material (40 deg.  C. would have been a better temperature).  Dr Weber determined