At the eleventh annual meeting of the representatives of the Bavarian chemical industries at Regensburg, attention was drawn to the unhealthy nature of the process of charging percussion caps.  Numerous miniature explosions occur, and the air becomes laden with mercurial vapours, which exercise a deleterious influence upon the health of the operatives.  There is equally just cause for apprehension in respect to the poisonous gases which are evolved during the solution of mercury in nitric acid, and especially during the subsequent treatment with alcohol.  Many methods have been proposed for dealing with the waste products arising during the manufacture and manipulation of fulminate of mercury, but according to Kaemmerer, only one of comparatively recent introduction appears to be at all satisfactory.  It is based upon the fact that mercuric fulminate, when heated with a large volume of water under high pressure, splits up into metallic mercury and non-explosive mercurial compounds of unknown composition.

In mixing the various ingredients with mercury fulminate to form cap mixtures, they should not be too dry; in fact, they are generally more or less wet, and mixed in small quantities at a time, in a special house, the floors of which are covered with carpet, and the tables with felt.  Felt shoes are also worn by the workpeople employed.  All the tools and apparatus used must be kept very clean; for granulating, hair sieves are used, and the granulated mixture is afterwards dried on light frames, with canvas trays the bottoms of which are covered with thin paper, and the frames fitted with indiarubber cushions, to reduce any jars they may receive.  The windows of the building should be painted white to keep out the rays of the sun.

Mr H. Maxim, of New York, has lately patented a composition for detonators for use with high explosives, which can also be thrown from ordnance in considerable quantities with safety.  The composition is prepared as follows:—­Nitro-glycerine is thickened with pyroxyline to the consistency of raw rubber.  This is done by employing about 75 to 85 per cent. of nitro-glycerine, and 15 to 25 per cent. of pyroxyline, according to the stiffness or elasticity of the compound desired.  Some solvent that dissolves the nitro-cotton is also used.  The product thus formed is a kind of blasting gelatine, and should be in a pasty condition, in order that it may be mixed with fulminate of mercury.  The solvent used is acetone, and the quantity of fulminate is between 75 to 85 per cent. of the entire compound.  If desired, the compound can be made less sensitive to shocks by giving it a spongy consistency by agitating it with air while it is still in a syrupy condition.  The nitro-glycerine, especially in this latter case, may be omitted.  In some cases, when it is desirable to add a deterring medium, nitro-benzene or some suitable gum is added.

[Illustration:  FIG. 34.  METHOD OF PREPARING THE CHARGE.]