110 



CHEMISTRY. (CHEMICAL PHYSICS.) 



pable of directly uniting do so only in the pres- 

 ence of at least" one other substance, chemists, 

 says II. I'- Armstrong, do not appear to have 

 arrived at any clear and consistent understand- 

 ing of the conditions determinative of chemical 

 change. In the discussion of a paper by Mr. H. 

 IJ. Baker on -Combustion in Dried Gases " in 

 1885, the author defined chemical action as re- 

 versed elect rnhixi*. the condition being that, in 

 ..rder that chemical action may take place, the 

 system operated on must comprise an electrolyte. 

 Hence, as neither oxygen, hydrogen, nor water 

 i> an electrolyte, a mixture of only the two gases 

 should not be explosive, and it was difficult to 

 understand how the presence of water pure and 

 simple should influence to produce an explo- 

 sion. These doubts have been verified. In such 

 cases, where action takes place, a trace of im- 

 purity is supposed to provide an electrolyte. 

 The author had once suggested that there might 

 be a difference between actions taking place at 

 low and high temperatures; but more attentive 

 consideration of the subject has led him to think 

 that this is not the case, and that we must treat 

 high temperature changes, so far as regards the 

 point under consideration, in the same way as 

 those occurring under ordinary conditions and 

 at low temperatures. The author fails to reach 

 any definite conclusions, but regards the whole 

 subject one of inquiry. Mr. V. H. Veley, after 

 four years' study of the conditions determinative 

 of chemical change, has come to the conclusion 

 that a century of work in chemical science has 

 brought no answer to the questions, What is the 

 nature of chemical change? and, What is the 

 cause of its commencement? " Of facts there is 

 no end, but no interpretation thereof." 



Taking as points of comparison the melting 

 points determined by M. Violle, viz., sulphur 

 448, gold 1,045, palladium 1,500, platinum 

 1,775 (all centigrade), M. H. le Chatelier finds 

 the melting point of white cast iron 1.135, of 

 gray cast iron 1,220, of mild steel 1,475, the 

 temperature of hard porcelain at the end of 

 a baking 1,370. The temperature of a normal 

 incandescent lamp is 1,800, but it may be pushed 

 to beyond 2, 100. Previous determinations have 

 been falsified by using for comparison the melt- 

 ing points of palladium and platinum. Thus 

 the temperature of the Bessemer process was 

 fixed by Langley at 2,000, because platinum 

 seemed to melt, rapidly in the flame. It does 

 not really melt, but merely dissolves in the mi- 

 nute drops of melted steel carried along in the 

 ga-eous current. 



In a paper at the British Association on "The 

 KfTec.t of Small Quantities of Foreign Matter 

 on the Properties of .Metals," Prof. Roberts-Aus- 

 ten said that the addition of two tenths per cent, 

 of lead or bismuth to gold was found to render 

 it brittle, while extremely small quantities of 

 phosphorus, magnesium, and zinc made nickel 

 malleable. Such phenomena had doubt u^s been 

 of great interest, in ancient, times to the alche- 

 mist, but to-day they constitute all-important 

 questions for the engineer. Experimenting on 

 gold, which could be obtained more readily 

 than most, other metals free from impurities, 

 either solid or gaseous, he had found that the 

 tenacity \va^ decreased by the addition of small 

 quantities of elements whose atomic volumes 



were greater than that of gold, while those 

 elements whose atomic volumes were the same 

 or smaller than that of gold increased its te- 

 nacity. Lithium and aluminium acted in an 

 exceptional manner. Furthermore, while the 

 addition of 10 per cent, of aluminium gave an 

 alloy melting at 400 lower than gold, a mixture 

 of 32 per cent, of aluminium yielded a brilliant 

 alloy having a higher melting point than gold. 

 Gold during the process of cooling showed ab- 

 normities similar to those shown by iron, which, 

 however, disappeared when the operation WHS 

 carried out under pressure. Prof. Hartley had 

 found that iron required to be slightly oxi- 

 dized before it could be melted, even at a tem- 

 perature which sufficed to melt platinum. He 

 had always found that silver and copper, unless 

 prepared with special precautions, which he de- 

 scribed, contained gold. 



In his studies on the rate of progress of chem- 

 ical change, Dr. J. H. Gladstone investigated 

 the reaction that takes place when platinum 

 chloride and potassium iodide are mixed, result- 

 ing in the formation of the dark-colored iodide. 

 The change begins rapidly, with no period of 

 inertness or "reluctance." Its completion is 

 much retarded, however, by the presence of po- 

 tassium chloride. The change that takes place 

 when cuprous oxide is immersed in a solution 

 of silver nitrate is one that requires time to at- 

 tain a maximum rate. The silver produced is 

 slow in making its appearance. 



In the investigations of J. W. Rodger and 

 Prof. Thorpe on the relations between the vis- 

 cosity of liquids and their chemical nature, in 

 which the method adopted allowed a rapid suc- 

 cession of experiments to be made on the same 

 liquid at different temperatures, evidence was 

 found, in the case of the fatty acids examined, 

 of the existence of molecular aggregates. 



According to the experiments of Dr. Brunck, 

 of Freiberg, polymeric oxygen or ozone is capa- 

 ble of formation and of subsequent existence for 

 a short time, even at temperatures of consider- 

 able elevation. It is true, as Andrews and Tait 

 have shown, that ozone is converted into ordi- 

 nary oxygen at 300 C., and Prof. Andrews has 

 given 237 C. as the temperature of dissociation ; 

 but Dr. Brunck has shown that the change is 

 not instantaneous, and that if the gas is allowed 

 to remain only a short time in the heated vessel 

 a considerable proportion escapes decomposition. 

 Several high temperature reactions are described 

 by the author in which oxygen is liberated to a 

 considerable extent in the condensed form of 

 ozone. Dr. Brunck further adduces experi- 

 mental evidence that the strongly odorous gas 

 hitherto regarded as chlorine, which is usually 

 admixed to a slight extent with the oxygen ob- 

 tained by heating a mixture of potassium chlo- 

 rate and manganese dioxide, is in reality ozone. 



Having previously found that, by a sufficient, 

 elevation of temperature, obtained by means of 

 the electric furnace, it is possible to effect in a 

 few moments the crystallization of metallic ox- 

 ides, the reduction of certain oxides, the fusion 

 of refractory metals, and the distillation of silica 

 and zirconia, INI. Moissan has further demon- 

 strated the volatilization of the metals and the 

 metallic oxides. With an apparatus which he 

 describes, the author proved, in the case of mag- 



