NA TURE 



^37 



THURSDAY, MAY 8, 1913. 



EXPLOSIVES AND PHYSICAL CHEMISTRY. 



Explosives : a Synoptic and Critical Treatment of 

 the Literature of the subject as gathered from 

 I arious Sources. By Dr. H. Brunswig-. Trans- 

 lated and annotated by Dr. Charles E. Munroe 

 and Dr. Alton L. Kibler. Pp. xv + 350. (New 

 York : John Wiley and Sons ; London : Chap- 

 man and Hall, Ltd., 1912.) Price 12s. 6d. 

 net. 



IN this volume Dr. Brunswig- attempts to direct 

 the study of explosives from the largely em- 

 pirical methods of the past into the more definite 

 fields of exact physical chemistry, in which the 

 nature, causes of explosion, and the controlling 

 conditions governing such phenomena naturally 

 fall. For this purpose he has collected the well- 

 known facts (and in many instances those fre- 

 quently overlooked) and arranged them in a 

 systematic manner. 



The earlier sections deal with the general char- 

 acter of explosive reactions, their velocity, pres- 

 sure, and temperature conditions, the character of 

 the gases evolved, explosion by influence, &c. 

 Judging by most of the literature on the subject, 

 the physico-chemical bearing of these important 

 matters is seldom considered, and Dr. Brunswig's 

 earlier chapters certainly emphasise the necessity 

 which exists for their receiving more considera- 

 tion, if progress is to be made. As the author 

 points out, "the days of purely empirical pro- 

 gress in the technology of explosives are num- 

 bered." 



Some comparisons of the energy content of 

 explosives (expressed as the heat of combustion) 

 with ordinary fuels are of interest. While 1 kilo- 

 gram of liquid petroleum develops 12,000 calories, 

 and average coal about 8000 calories, dynamite 

 (with 25 per cent, kieselguhr) only develops 1300 

 calories. " Explosives are only technically valu- 

 able because they liberate all their energy in a 

 very short space of time." The actual utilisation 

 of this energy, according to the author, by no 

 means compares favourably with that in a high- 

 class engine, such as the Diesel type. The effi- 

 ciency of such engines is given as 32 per cent. 

 (37 would be a better figure), whilst with 

 most explosives the available energy is calcu- 

 lated to be only 15 to 20 per cent, of the 

 theoretical. 



The misleading relative value of explosives of 

 widely different character which may be deduced 

 simply from the heat of combustion, or the pro- 

 NO. 2271, VOL. 91] 



duct of the gaseous volume and temperature 

 attained (the characteristic product, or potential 

 energy), is evident from the following figures, from 

 tables in the book, when explosive gelatine is 

 taken as 100. 



Comparative value 



Mercury fulminate ... 25 11 



As the author points out, such misleading 

 figures — which place, for example, mercury ful- 

 minate below powder — are due to the omission of 

 the velocity with which the reactions take place. 

 In this connection it should be mentioned that in 

 Noble's classical work with modern smokeless 

 powders, this reaction velocity would not be 

 greatly different for the various explosives he 

 dealt with, and the relative potential energy figures 

 would be unaffected. 



The second portion of the book, dealing with the 

 characteristics and manufacture of the principal 

 explosives, will convey little fresh information to 

 those already somewhat familiar with the subject. 

 Dr. Brunswig says that he has "refrained from 

 mentioning other material which has become 

 known to him through personal relation with the 

 technique of explosives," and pleads "the restrain- 

 ing influence of industrial discretion," where con- 

 tradiction exists between literature and personal 

 knowledge of the facts. 



In the list of important propellants, brown 

 prismatic powder and amide powder appear as 

 "great-gun powders," and ordinary black powder 

 as a musket powder. It would be of interest to 

 learn who is still employing them for these pur- 

 poses. Again, M.D. cordite is classed as a musket 

 powder, but is not included in the big-gun 

 powders. 



Erosion is one of the most important questions 

 relating to propellant explosives. The author 

 quotes Sivy's statement that one-third of a kilo- 

 gram of iron is lost with every shot from an effi- 

 cient 28 cm. gun. The reader might, however, find 

 difficulty in deciding on the primary cause. In 

 one place it is stated that the percentage of nitro- 

 glycerin originally present in the earlier ballistites 

 and cordites was reduced (a change intended solely 

 to reduce erosion) because the explosive contained 

 too much nitrogen. It must not be inferred that 

 the true reason for erosion, the high temperatures 

 resulting from the high proportion of carbon 

 dioxide formed, is overlooked, but this primary 



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