Although very great cart: is exercised in the manufacture of gunpowder, yet there are so many opportunities for variations to occur in each of the many steps of the process that even the best powder-makers cannot regularly pro duce powder that will always give the same pressure and velocity in the same gun. Since, in order to ensure accuracy of fire, the suc cessive powder charges used must possess the same ballistic properties this result is secured by proving a number of factory runs by firing trials and then mixing these together in the proportions required to produce the desired re sult. This process is called blending. It was practised by Benvenuto Cellini and has been in vogue ever since.
Good black gunpowder should have a per fectly uniform slate color and it should show no difference in color when crushed. If it is bluish or quite black it contains too much char coal or is too damp, while the presence of bright points of bluish-white spots indicates that the saltpeter has effloresced. If the pow der soils the hand or a sheet of paper when run over them it contains too much moisture or else meal powder. On pressing the powder in the hand it should not crackle or be easily crushed and when crushed the grains should not fall at once to dust, but should first split into angular fragments. Three different den sities are determined for gunpowder, each of which furnishes valuable information. These are the gravimetric density which is the weight of a unit volume of powder grains including the air between and enclosed in them; the rela tive density, which is the weight of a unit volume of powder grains excluding the air be tween them but including that contained in the pores of the grains; and the absolute specific gravity, which is the weight of the powder ex clusive of all air.
Since smokeless gunpowder has been per fected and adopted for use in guns of all cali bres it has to a large extent superseded black gunpowder; yet the production of black gun powder bids fair to continue for many years to come, because in ordnance it is necessary to use a priming charge of it with which to fire the smokeless gunpowder; because smokeless pow der cannot be efficiently substituted for black gunpowder in the older forms of small arms that are widely scattered over the country; be cause black powder is most suitable for use in fuses and in pyrotechny; and because smoke less powder is too expensive and inferior for use in saluting.
Gunpowder was formerly used in blasting as well as for a propellent, but usually a special mixture containing as little as 60 per cent of saltpeter was prepared for this purpose. In 1857 Lamotte Dupont of Wilmington, Del., in vented blasting powder which differs from gun powder chiefly in that Chile saltpeter is used in place of India saltpeter. Though crude ma terials are used and less care is taken the methods pursued for its manufacture are in general similar to those used for gunpowder.
Bibliography.— Anderson, W.,