PEOGEESS IN EXPLOSIVES GUTTMANN. 275 



day. The contents of the tank froze and required two days to thaw ; 

 a yield of 240 parts nitroglycerin was, however, the surprising result. 



With regard to the selection of apparatus, round lead or steel 

 tanks, as explained above, are generally used, but the author has also 

 seen square-cornered ones. The x\mericans are much in favor of 

 mechanical stirring, whilst in Europe air stirring is preferred. Hav- 

 ing worked with both, I can not see much difference as regards re- 

 sults, but since I do not like to have any moving parts in connection 

 with the manufacture of nitroglj'cerin I think air stirring is pref- 

 erable, on the whole. 



There has been no special improvement in the manufacture of 

 dynamite since Nobel in 1875 invented blasting gelatin. 



In this connection it will be interesting to have a true picture of 

 kieselguhr as used for dynamite. Mr. Henry de Mosenthal, whose 

 skill in preparing specimens for the microscope we had often occa- 

 sion to admire, has prepared for me various slides of kieselguhr. 



For blasting gelatin, as you know, a so-called " collodion cotton " 

 or soluble nitrocellulose is employed. Many i^eople think that if 7 

 per cent of nitrocellulose is insufficient to make a stiff and suitable 

 blasting gelatin, the addition of another 1 or 2 per cent would do it, 

 and certainly at first the resulting gelatin is so stiff and hard as to 

 require special effort in the cartridge machines. After a few months 

 of storage, however, or after passing over the equator into Australia, 

 nitroglycerin is found to exude. A good nitrocellulose will give a 

 perfectly stiff blasting gelatin, with between 6 and 7 per cent of 

 nitrocotton, and if a 2^ per cent solution is made in a porcelain basin, 

 the resulting gelatine should be easily detachable after cooling, show- 

 ing no signs of exudation. 



There has been within recent years a revival of old ideas, but with 

 better success, for the purpose of obviating one of the chief objections 

 to dynamite, namely, that of freezing. It was in 1860, in Sweden, 

 that A. E. Rudberg patented the addition of nitrobenzine to nitro- 

 glycerin for the purpose of making it unfreezable.'^ The Societe 

 des Poudres et Dj^namites, of Arendonck, found later ^ that the addi- 

 tion of dinitrotoluene dissolved in nitroglycerin was very useful in 

 lowering the freezing point. A new departure was really made when 

 Dr. Anton Mikolajczak in 1904 patented the addition of dinitro- 

 glycerin to trinitroglycerin explosives, and at the same time indicated 

 a practical method of manufacturing it.'' It is now made on a large 

 scale in a factory at Castrop, in Germany. In order to understand 

 the question better it is necessary to point to a most interesting work 



« Swedish patent, April 30, 1866. 

 6 British patent. No. 14827, of 1903. 

 '^ Id,, No. 8041, of 1904. 



