4. When a sufficient quantity of these grains are procured, they are put into another drum, of a suitable size, with one and a half times their weight of the original mixture. The drum being put in motion, some water is added, which serves to make them increase in size, by constant rubbing: at the end of a certain time, the whole becomes granulated, or perfectly round. The density of the grains depends on the mixture, and the time they were kept in motion.
5. The powder being thus grained, is passed through sieves, whose holes are of different diameters; and hence it is divided into three kinds: viz. cannon powder, musket powder, and fine grained powder.
6. Finally, the powder is dried, and preserved in the usual manner. Its strength is equal to that made by the old process, and is perfectly round.
It may be proper to observe, that this process presents many important and decided advantages. Although, in our description, we have not gone into details, yet the whole operation will be seen at one view. It was practised in France, by its inventor, M. Champy, and, besides being introduced into the United States, it has also been adopted in Prussia.
M. Proust endeavoured to show, that charcoal made of shoots or branches, makes the best powder, and will mix with more facility with the nitre and sulphur; and in employing the ordinary charcoal, two hours beating is necessary to obtain a perfect mixture. The pestles, as Chaptal observes, usually make fifty-five strokes in a minute. Their weight is various; he gives them at eighty pounds.
M. Carney discovered a new process for the fabrication of powder, and although Chaptal himself made some advantageous changes in the process, yet the merit of the discovery he gives entirely to Carney. The process of M. Champy, is in some particulars the same. It will be sufficient, however, to observe, that it is reduced to three heads: viz.
1. The pulverization, and sifting of the materials;
2. Mixing the materials intimately in vessels similar to casks; and,
3. Giving the mixture the necessary consistence, and the final granulation.
For some details of the process, the reader may consult Chaptal's Chimie Appliqué aux Arts, tome iv, p. 145.