| 165-177 " No. 5 " " | 205-217 __________________________________________________________|__________ | | | deg.C. | Powder used in Chassepot rifle | 191 | By Leygue & Champion. French gunpowder | 295 | " " Rifle powder (picrate) | 358 | " " Cannon | 380 | " " __________________________________|_________|________________________ Horsley's apparatus consists of an iron stand with a ring support, holding a hemispherical iron vessel or bath in which solid paraffin is put. Above this is another movable support, from which a thermometer is suspended, and so adjusted that its bulb is immersed in the material contained in the iron vessel. A thin copper cartridge-case, 5/8 inch in diameter and 1-15/16 inch long, is suspended over the bath by means of a triangle, so that the end of the case is just 1 inch below the surface of the molten material. On beginning the experiment of determining the firing point of any explosive, the material in the bath is heated to just above the melting point; the thermometer is inserted in it, and a minute quantity of the explosive is placed in the bottom of the cartridge-case. The initial temperature is noted, and then the cartridge-case containing the explosive is inserted in the bath. The temperature is quickly raised until the contents of the cartridge-case flash off or explode, when the temperature is noted as the _firing point_. [Illustration: FIG. 46.--HEAT TEST APPARATUS.] Professor C.E. Munroe, of the U.S. Torpedo Station, has determined the firing point of several explosives by means of this apparatus. ~The Government Heat Test (Explosives Act, 1875): Apparatus required.~--A water bath, consisting of a spherical copper vessel _(a)_, Fig. 46, of about 8 inches diameter, and with an aperture of about 5 inches; the bath is filled with water to within a quarter of an inch of the edge. It has a loose cover of sheet copper about 6 inches in diameter _(b)_ and rests on a tripod stand about 14 inches high _(c)_, which is covered with coarse wire gauze _(e)_, and is surrounded with a screen of thin sheet copper _(d)_. Within the latter is placed an argand burner _(f)_ with glass chimney. The cover _(b)_ has four holes arranged, as seen in Fig. II., No. 4 to contain a Page's[A] or Scheibler's regulator, No. 3 the thermometer, Nos. 1 and 2 the test tubes containing the explosive to be tested. Around the holes 1 and 2 on the under side of the cover are soldered three pieces of brass wire with points slightly converging (Fig. III.); these act as springs, and allow the test tubes to be easily placed in position and removed. [Footnote A: See _Chem. Soc. Jour._, 1876, i. 24. F.J.M. Page.]