Upon leaving the filter house, where it has been washed and filtered, and has satisfactorily passed the heat test, it is drawn off from the lowest tank in indiarubber buckets, and poured down the conduit leading to the precipitating house, where it is allowed to stand for a day, or sometimes longer, in order to allow the little water it still contains to rise to the surface. In order to accomplish this, it is sufficient to allow it to stand in covered-in tanks of a conical form, and about 3 or 4 feet high. In many works it is previously filtered through common salt, which of course absorbs the last traces of water. It is then of a pale yellow colour, and should be quite clear, and can be drawn off by means of a tap (of vulcanite), fixed at the bottom of the tanks, into rubber buckets, and is ready for use in the preparation of dynamite, or any of the various forms of gelatine compounds, smokeless powders, &c., such as cordite, ballistite, and many others. Mikolajezak (_Chem. Zeit._, 1904, Rep. 174) states that he has prepared mono- and di-nitro-glycerine, and believes that the latter compound will form a valuable basis for explosives, as it is unfreezable. It is stated to be an odourless, unfreezable oil, less sensitive to percussion, friction, and increase of temperature, and to possess a greater solvent power for collodion-cotton than ordinary nitro-glycerine. It can thus be used for the preparation of explosives of high stability, which will maintain their plastic nature even in winter. The di-nitro-glycerine is a solvent for tri-nitro-glycerine, it can therefore be mixed with this substance, in the various gelatine explosives in order to lower the freezing point.