February 3, 19 16] 



NATURE 



639 



other of them may usually be found in a chlorate 

 blasting explosive. The addition of aluminium greatly 

 increases the heat of explosion ; it is present in the 

 explosives of the ammonal type, 



NiTRO-AROMATic COMPOUNDS. — Modern high explo- 

 sives very frequently contain nitro-derivatives of the 

 aromatic compounds obtained from coal tar, especially 

 the mono- di- and tri-nitro-derivatives of benzene, 

 toluene, and naphthalene. The nitro-groups in these 

 compounds contribute oxygen for the explosive re- 

 action. The trinitro-compounds of substances con- 

 taining only one benzene ring are explosives in them- 

 selves ; trinitrotoluene, for instance. Trinitrotoluene is 

 not only a constituent of composite explosives, but is 

 also very largely used by itself as a charge for shell 

 and submarine mines, and for other military and 

 naval purposes, for which Its insensitiveness combined 

 with its great violence render it suitable. Picric acid 

 (trinitrophenol) is also much used for these purposes, 

 and trinitrocresol to a less extent. Although they 

 detonate with great violence, these trinitro-compounds 

 do not contain sufficient oxygen to oxidise the whole 

 of the carbon they contain even to the stage of carbon 

 monoxide. Their power as explosives is, therefore, in- 

 creased by mixing them with oxygen carriers. Com- 

 mercial explosives containing trinitrotoluene always 

 have also some other constituent which can supply 

 the deficient oxygen. 



Nitric Esters. — Nitroglycerin and the nitro- 

 celluloses are the principal members of another very 

 important group of substances that can be used as 

 explosives without admixture. Strictly speaking, they 

 are not nitro-derivatives, but nitric esters. The more 

 highly nitrated celluloses, such as guncotton, contain 

 enough oxygen to convert all the hydrogen into water 

 and the carbon into monoxide, and even some of it 

 into dioxide. Nitroglycerin, CHjNjO,, not only has 

 enough to oxidise entirely all its hydrogen and carbon, 

 but also has a little oxygen left over. Nitroglycerin 

 is the most powerful explosive compound known, but 

 its power is increased by dissolving in it a small 

 proportion of nitrocellulose, which utilises the excess 

 of oxygen and at the same time converts it into a 

 gelatinous solid known as blasting gelatin. 



Smokeless Powders. — All smokeless powders con- 

 sist largely of nitrocellulose, which has been more or 

 less gelatinised and converted into a compact colloid 

 by means of a suitable solvent ; many of them contain 

 practically nothing else, but in others there is a con- 

 siderable proportion of nitroglycerin. Small per- 

 centages of mineral jelly, inorganic nitrates, and other 

 substances are also added, in many cases to improve 

 the ballistics or the stability. Powders for rifled arms 

 are always colloided as completely as possible, whether 

 they be for small-arms or ordnance, to make them 

 burn slowly and regularly, but in shot-gun powders 

 the original structure of the nitrocellulose is not 

 always destroyed entirely, as they are required to 

 burn comparatively rapidly. 



Endothermic Compounds. — There are some explo- 

 sive compounds which do not depend at all for their 

 action on oxidation or reduction. These are endo- 

 thermic substances, which decompose with the evolu- 

 tion of gas and heat ; they are usually rather sensitive. 

 The only compounds of this class that are of commer- 

 cial importance are fulminate of mercury, Hg(CNO)j, 

 and lead azide, PbN«, both of which are used only 

 for exploding other explosives. 



Velocity of Explosion.— The heat and gas evolved 

 are the two principal factors which govern the power 

 of an explosive, i.e. the amount of work it can do in 

 the way of displacing objects. But the time taken 

 by the- explosion is also a matter of great importance. 

 TThe rate of explosion is measured by making a column 

 of the explosive, confining it, if necessary, in a metal 

 NO. 2414, VOL. 96] 



I tube, and measuring the time that the explosive wave 

 ' takes to travel a known distance. In black powder 

 I and similar nitrate mixtures the velocity of explosion 

 J is only a few hundred metres a second, but with 

 modern high explosives the velocity of detonation is 

 from two to seven thousand metres a second. This 

 naturally makes them much more violent and de- 

 structive. Explosives of the gunpowder type are used 

 T^when earth or soft rock is to be blasted, or when the 

 1 material must not be broken up too much. Propellants 

 for use in firearms are required to burn slowly; for 

 rifled arms they must be slower even than gunpowder. 

 I They are not exploded by means of another high 

 I explosive, but merely lit by a powerful flame, and 

 should then burn by concentric layers. The rate of 

 ! burning increases with the pressure in the gun, but for 

 completely gelatinised powders it is less than a metre 

 ! a second. A. Marshall. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 i The Scottish Association for the Medical Education 

 i of Women has placed with the authorities of the 

 I University of Edinburgh the sum of 237Z. for the pur- 

 ' pose of founding a prize for women medical students. 

 ! The Foulis memorial scholarship of the University 

 of Glasgow has been awarded to Dr. John Cruick- 

 shank, pathologist to the Crichton Royal Institution, 

 Dumfries, for distinction in original work in patho- 

 logy. 



It is announced in the issue of Science for January 

 14 that four business men of Portland have contri- 

 buted 5oooi. toward the new buildings for the medical 

 department of the University of Oregon, Portland. 

 This makes available the lo.oooZ. appropriated by the 

 State. The officers of the college now propose to 

 raise an additional 2o,oooi. 



The issue of the Pioneer Mail for January i contains 

 a report of the eleventh session of the Indian Indus- 

 trial Conference, which commenced its sittings on 

 December 24 last. It was the first time the conference 

 had met in Bombay since its inception. There was 

 an unusually large attendance of delegates and distin- 

 guished visitors. The president. Sir Dorabji J. Tata, 

 is one of the pioneers of Indian industry. In the 

 course of his address, he referred to the importance 

 of industrial education, and said industrial education 

 in the widest sense of the term is primarily the func- 

 ! tion of the State. But a good many people wish the 

 State to go far beyond this rdle and to enter into the 

 actual field of industrial enterprise. The president's 

 message to the Congress, and through it to his country- 

 men, was "Educate, Organise, Co-operate." Scien- 

 I tific, technical, economic education is the function of 

 the State, but he said they must take their share of 

 the burden. If they really wanted higher scientific 

 ; education and were determined to profit by it, they 

 would get it. Dr. H. H. Mann, principal of the Agri- 

 cultural College, moved a resolution earnestly recom- 

 mending the establishment of a technological faculty 

 at the principal Indian universities, the development 

 of already existing technical institutions, the opening 

 of new institutions, and the gradual introduction of 

 technical instruction in primary and secondary schools. 

 The resolution, which was adopted, appealed to men 

 of capital and industry to help young Indians technic- 

 ally trained in finding practical work and employment. 

 There is a widespread opinion among competent 

 authorities that an independent inquiry should be made 

 into our system of education, particularly as regards 

 I its organisation, the powers of the Board of Educa- 

 I tion, the relations of the Board to local education 



