into 100 parts of para-nitro-toluene, while the latter is kept at a temperature between 60 deg. to 65 deg.  C., and continually stirred.  When the acid has all been run in, this mixture is heated for half an hour to 80 deg.  C., and allowed to stand till cold.  The excess of nitric acid is then removed.  The residue after this treatment is a homogeneous crystalline mass of ortho-para-di-nitro-toluene, of which the solidifying point is 69.5 deg.  C. To convert this mass into tri-nitro derivative, it is dissolved by gently heating it with four times its weight of sulphuric acid (95 to 96 per cent.), and it is then mixed with 1-1/2 times its weight of nitric acid (90 to 92 per cent.), the mixture being kept cool.  Afterwards it is digested at 90 deg. to 95 deg.  C., with occasional stirring, until the evolution of gas ceases.  This takes place in about four or five hours.

The operation is now stopped, the product allowed to cool, and the excess of nitric acid separated from it.  The residue is then washed with hot water and very dilute soda solution, and allowed to solidify without purification.  The solidifying point is 70 deg.  C., and the mass is then white, with a radiating crystalline structure.  Bright sparkling crystals, melting at 81.5 deg.  C. may, however, be obtained by recrystallisation from hot alcohol.  The yield is from 100 parts di-nitro-toluene, 150 parts of the tri-nitro derivative.  Haeussermann states also that 1:2:4:6 tri-nitro-toluene can be obtained from ordinary commercial di-nitro-toluene melting at 60 deg. to 64 deg.  C.; but when this is used, greater precautions must be exercised, for the reactions are more violent.  Moreover, 10 per cent. more nitric acid is required, and the yield is 10 per cent. less.  He also draws attention to the slight solubility of tri-nitro-toluene in hot water, and to the fact that it is decomposed by dilute alkalies and alkaline carbonates—­facts which must be borne in mind in washing the substance.  This material is neither difficult nor dangerous to make.  It behaves as a very stable substance when exposed to the air under varying conditions of temperature (-10 deg. to +50 deg.  C.) for several months.  It cannot be exploded by flame, nor by heating it in an open vessel.  It is only slightly decomposed by strong percussion on an anvil.  A fulminate detonator produces the best explosive effect with tri-nitro-toluene.  It can be used in conjunction with ammonium nitrate, but such admixture weakens the explosive power; but even then it is stated to be stronger than an equivalent mixture of di-nitro-benzene and ammonium nitrate.  Mowbray patented a mixture of 3 parts nitro-toluol to 7 of nitro-glycerine, also in the proportions of 1 to 3, which he states to be a very safe explosive.

Faversham Powder.—­One of the explosives on the permitted list (coal mines) is extensively used, and is manufactured by the Cotton Powder Co.  Ltd. at Faversham.  It is composed of tri-nitro-toluol 11 parts, ammonium nitrate 93 parts, and moisture 1 part.  This explosive must be used only when contained in a case of an alloy of lead, tin, zinc, and antimony thoroughly waterproof; it must be used only with a detonator or electric detonator of not less strength than that known as No. 6.