94 SEC. 3. MEASUREMENT. 



DETERMINATION OF THE SPECIFIC WEIGHT OF THE POWDER TO BE 



TESTED. 



The prisms or pieces of cake, or the coarse or fine-grained powder to be 

 tested, are accurately weighed on a scale. 



The powder prisms of 25 mm. height, 40 mm. measured across the edges, 

 35 mm. on two sides, with channels each of 4-2 4 f mm. wide, or one chan- 

 nel 10 mm. wide, weigh, as a rule, at a specific weight of 1 '6 to 1'8, from 36 

 to 44 grammes. 



Of grained powder so much is weighed that the steel lid can be easily fixed 

 on the reservoir, and fastened with the bolt, consequently about 50 grammes 

 in case of a small reservoir with about 76 cub. cent, capacity, or 200 gr. in 

 case of a larger reservoir of about 217 226 cub. cent, capacity. The 

 quantity of powder weighed is filled into the reservoir ; this is then closed, 

 the two hoses 1 and 2 are screwed on, and the operation is thereupon 

 proceeded with as detailed in the preceding explanations. 



It must be observed that the operation is very simple and expeditious, 

 excluding every personal error, so that, consequently, the method, being 

 based on scientific principles, is a thoroughly rational one. 



It should cause no surprise if the operations 1 and 2 must be repeated several 

 times, when the powder has been filled in, in order to raise the difference of 

 the level of the two mercury columns to the same height as the position of 

 the barometer, as the large capacities of the coal of the powder for absorbing 

 air is a notorious fact, and as also the moisture contained in the powder is 

 to a very great extent evaporated in the form of aqueous vapour, or ejected 

 by hydrostatic pressure and tension. 



373. Mercurial Powder Balance, Major Bode's con- 

 struction, for determining the specific gravity of prismatic and 

 coarse-grained gunpowders. A. and R. Hahn, Cassel. 



The mercurial powder scale replaces the alcohol or so-called " volumetrical 

 analysis method," and by means of this instrument the specific weight of 

 the different sorts of powder, prismatic, powder-cake, and coarse-grained 

 can be exactly determined with quantities of 40 to 50 grammes. 



380. Balance for Weighing in Vacuo. 



Paul Bunge, Hamburg. 



The vacuum scale is a duplicate of a similar scale made by the exhibitor 

 for the Physiological Institute at Kiel. For facilitating exhaustion it has 

 been enclosed in a small receiver of 5 inches diameter and 10 inches in 

 height, which was only possible by the exhibitor's system of employing a 

 short beam. This is 69 millimeters long, and Avith a load of 50 gr. the 

 balance turns with -$ mgr. 



The use of the scales is as follows : After the body which is to be weighed 

 in dried air or in a vacuum has been placed on the scales, and the exhaustion 

 or the desiccation has been effected, the scale can be arrested and released 

 by turning three studs fixed in the bottom plate. All weights of 20 gr. to 

 0-01 gr. can be placed on or lifted off the pan. Lastly, a rider can be tra- 

 versed the whole length of a beam in the line of the axis. 



