Part 21 (2/2)

Professor CE Munroe, of the US Torpedo Station, has deter 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 ater to within a quarter of an inch of the edge It has a loose cover of sheet copper about 6 inches in diah _(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 chi II, No

4 to contain a Page's[A] or Scheibler's regulator, No 3 the ther the explosive to be tested Around the holes 1 and 2 on the under side of the cover are soldered three pieces of brass ith 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 _Chee]

~Test Tubes~, fro, and of such a diameter that they will hold froht of 5 inches; rather thick glass is preferable Indiarubber stoppers, fitting the test tubes, and carrying an arrangelass tube passing through the centre of the stopper, and terlass rod drawn out and the end turned up to fore from 30 to 212 F, or from 1 to 100 C A minute clock is useful

~Test Paper~--The test paper is prepared as follows:--45 grains (29 grms) of white maize starch (corn flour), previously washed with cold water, are added to 8-1/2 oz of water Thefor ten rm) of pure potassium iodide (previously recrystallised from alcohol, absolutely necessary) are dissolved in 8-1/2 oz of distilled water The two solutions are thoroughly lish filter paper, previously washed ater and re-dried, are dipped into the solution thus prepared, and allowed to remain in it for not less than ten seconds; they are then allowed to drain and dry in a place free froins of the strips or sheets are cut off, and the paper is preserved in well- stoppered or corked bottles, and in the dark The dimensions of the pieces of test paper used are about 4/10 inch by 8/10 inch (10 mm by 20 mm)[A]

[Footnote A: When the paper is freshly prepared, and as long as it reood condition, a drop of diluted acetic acid put on the paper with a glass rod produces no coloration In process of time it will become brownish, when treated with the acid, especially if it has been exposed to sunlight It is then not fit for use]

In Germany zinc-iodide starch paper is used, which is considered to be more sensitive than potassium iodide

~Standard Tint Paper~--A solution of caramel in water is made of such concentration that when diluted one hundred times (10 cc made up to 1 litre) the tint of this diluted solution equals the tint produced by the Nessler test in 100 cc water containing 000075 grrm AmCl With this caramel solution lines are drawn on strips of white filter paper (previously ashed with distilled water, to re matter, and dried) by means of a quill pen

When the marks thus produced are dry, the paper is cut into pieces of the same size as the test paper previously described, in such a way that each piece has a brown line across it near the th, and only such strips are preserved in which the brown line has a breadth varying from 12 mm to 1Dynalycerine preparations, frolycerine can be extracted in thetest, otherwise they will not be considered as lycerine,” viz, fifteen minutes at 160 F (72 C)

~Apparatus required~--A funnel 2 inches across (_d_), a cylindrical47

~Mode of Operation~--About 300 (194 grrms) of dynamite (_b_), finely divided, are placed in the funnel, which is loosely plugged by freshly ignited asbestos (_a_) The surface is slass rod or stopper, and souhr (_c_) is spread over it to the depth of about 1/8 inch

Water is then poured on from a wash bottle, and when the first portion has been soaked up lycerine has collected in the graduated h, it lycerine by filter paper, or the nitro-glycerine may be filtered

[Illustration: FIG 47--APPARATUS FOR SEPARATING THE NlTRO-GLYCERINE FROM DYNAMITE]

[Illustration: FIG 48--TEST TUBE ARRANGED FOR HEAT TEST]

~Application of Test~--The therh the lid of the water bath into the water, which is maintained at 160 F (72 C), to a depth of 2-3/4 inches Fifty grains (= 329 grhed into the test tube, in such a way as not to soil the sides of the tube (use a pipette) A test paper is fixed on the hook of the glass rod, so that when inserted into the tube it will be in a vertical position A sufficient alycerine, to moisten the upper half of the paper, is now applied to the upper edge of the test paper by lass rod or ca the rod and paper is fixed into the test tube, and the position of the paper adjusted so that its lower edge is about half way down the tube; the latter is then inserted through one of the holes in the cover to such a depth that the lower in of the moistened part of the paper is about 5/8 inch above the surface cover The test is complete when the faint brown line, which after a time makes its appearance at the line of boundary between the dry and moist part of the paper, equals in tint the brown line of the standard tint paper

~Blasting Gelatine, Gelatine Dyna gelatine are intir the two ether with a wooden pestle in a wooden radually introduced into the test tube, with the aid of gentle tapping upon the table between the introduction of successive portions of the mixture into the tube, so that when the tube contains all the mixture it shall be filled to the extent of 1-3/4 inch of its height The test paper is then inserted as above described for nitro-glycerine The sample tested must stand a temperature of 160 F for a period of tena discoloration of the test paper corresponding in tint to the standard paper

_NB_--Non-gelatinised nitro-glycerine preparations, frolycerine cannot be expelled by water, are tested without any previous separation of the ingredients, the te seven minutes

~Gun-Cotton, Schultze Gunpowder, EC Powder, &c: A Compressed Gun- Cotton~--Sufficient material to serve for two or entle scraping, and if necessary, further reduced by rubbing between the fingers The fine powder thus produced is spread out in a thin layer upon a paper tray 6 inches by 4-1/2 inches, which is then placed inside a water oven, kept as nearly as possible at 120 F (49 C) The wire gauze shelves of the oven should be about 3 inches apart The sample is allowed to remain at rest for fifteen minutes in the oven, the door of which is left wide open After the lapse of fifteen minutes the tray is removed and exposed to the air of the roo at some point within that time rubbed upon the tray with the hand, in order to reduce it to a fine and uniform state of division

The heat test is performed as before, except that the teulator set to rently pressed down until it occupies a space of as nearly as possible 1-5/10 inch in the test tube of di to the sides of the tube can be removed by a clean cloth or silk handkerchief The paper is e with a drop of the 50 per cent glycerine solution, the tube inserted in the bath to a depth of 2-1/2 inches,inserted to the same depth The test paper is to be kept near the top of the test tube, but clear of the cork, until the tube has been i of moisture will about this time be deposited upon the sides of the test tube, a little above the cover of the bath The glass rod in of the moistened part of the paper is on a level with the botto of moisture in the tube The paper is now closely watched, The test is complete when a very faint brown coloration makes its appearance at the line of boundary between the dry and moist parts of the paper It must stand the test for not less than ten minutes at 170 F

(The time is reckoned from the first insertion of the tube in the bath until the appearance of a discoloration of the test paper)

~B Schultze Powder, EC Powder, Collodion-Cotton, &c~--The sample is dried in the oven as above for fifteen minutes, and exposed for two hours to the air The test as above for coun-cotton is then applied

~C Cordite~ must stand a temperature of 180 F for fifteen minutes The sa are cut from one end of every stick selected for the test: in the case of the thicker cordites, each piece so cut is further subdivided into about four portions These cut pieces are then passed once through the h being rejected on account of the possible presence of foreign round material is put on the top sieve of the nest of sieves, and sifted That portion which has passed through the top sieve and been stopped by the second is taken for the test If the round material will be of the proper size If the volatile matter in the explosive exceeds 05 per cent, the sifted140 F, until the proportion does not exceed 05 per cent After each saround, the mill must be taken to pieces and carefully cleaned The sieves used consist of a nest of two sieves with holes drilled in sheet copper The holes in the top sieve have a diameter = 14 BWG, those in the second = 21 BWG

If too hard for the mill, the cordite may be softened by exposure to the vapour of acetone,[A] or reduced, to the necessary degree of subdivision by means of a sharp moderately-coarse rasp Should it have become too soft in the acetone vapour for the mill, it should be cut up into sree of hardness by sielatinised collodion-cotton, and partly of ungelatinised gun-cotton, are best reduced to powder by a rasp, or softened by exposure to mixed ether and alcohol vapour at a temperature of 40 F to 100 F

[Footnote A: Mr W Cullen _(Jour Soc Chem Ind_, Jan 31, 1901) says:-- ”Undoubtedly the advent of the horny smokeless powders of ive the test the same scope as it had when first introduced” As a rule a simple explanation can be found for every apparently abnormal result, and in the accidental retention of a portion of the solvent used in the manufacture, will frequently be found an explanation of the trouble experienced]