76 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 at 0-01 grammes. 



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, contents of 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 hereby that the operation is very simple and expeditious, 

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

 based on scientific principles, is a thorough rational one. 



It should cause no surprise if the momenta 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 capabilities of the coal of the powder of absorbing 

 the 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. ffahn, Cassel. 



The mercurial powder scale supplants the alcohol or so-called " volu-metri- 

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

 of the different sorts of powder, viz., 1, prismatic ; 2, powder-cake ; and 3, 

 coarse-grained powder, can be exactly determined in 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 for the Physio- 

 logical Institute at Kiel. For facilitating the evacuation it has been fitted 

 into a small space of 5 inches diameter and 10 inches in height, which was 

 only possible by the exhibitor's system of employing short balances (beams). 

 The latter is 69 millimeters long, and is at a weight of 50 gr. sensible at the 

 rate of^mgr. 



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

 in the rarified space, or to be exsiccated, has been placed on the scales, and 

 the evacuation or the exsiccation has been effected, the scale can be arrested 

 and released by means of three corks fixed in the bottom plate by appro- 

 priately turning the same. All weights of 20 gr. to 0-01 gr. can be placed 

 on or lifted off the frame supplying the weight scale. Lastly, a block can be 

 slided along the whole length of a ruler in the line of the axis. 



