upon Gun+powder , &c. ^27 
I was willing to fee the effefl of mixing fait of tartar with gun- 
powder, and accordingly having provided forhe of this alkaline 
fait initspureft ftate, thoroughly dry, and in a fine powder, I 
mixed 20 grains of it with 145 grains of gun-powder; and 
upon difcharging a bullet with the mixture, I found that the 
alkaline fait had confiderably leflened the force of the powder. 
See experiment N° 78. 
I next made ufe of fal ammoniacum. That fait has been: 
found to produce a very large quantity of elaftic air, or vapour* 
when expofed to heat under certain circum fiances ; but when 
20 grains of it were mixed with a charge of gun - powder, in- 
ftead of adding to its force, it diminilhed it very fenfibly. See 
the 80th experiment. 
Moft, if not all, the metals, are thought to produce large 
quantities of air when they are diflolved in proper m.enpirua^ and 
particularly brafs, when it is diilblved in fpirit of nitre. De- 
firous of feeing if this could be done by the flame, or acid 
vapour of fired powder, I mixed 20 grains of brafs in a very 
fine powder, commonly called brafs duft (being the fmall 
particles of this metal that fly off from the wheel in (harpening 
pins), with 145 grains of powder, and with this compound 
and a fit bullet I loaded my barrel and difcharged it ; but the 
experiment (N° 81.) fhewed, that the force of the powder was 
not increafed by the addition of the brafs duft, but the con- 
trary. 
It feems probable, however, that neither brafs duft nor 
aethiops mineral are of themfelves capable of diminifhing the 
force of gun-powder in any confiderabledegree, otherwife than-, 
by filling up the interftices between the grains, and obftru&ing 
the paflage of the flame, and fo impeding the progrefs of the in- 
flammation. And hence it appears, how earthy particles and 
X x -2 impurities 
