MICHAEL FAEADAY — HIS LIFE AND WORKS. 



231 



The discovery of tliis bicarbm-et of hydrogen was only an incident in the 

 reseai'ches which Faraday had undertaken in 1S23, upon the condensation of 

 gases into liquids. His mode of operation in this investigation consisted in 

 placing in one extremity of a recui-ved tube, closed at both ends, the necessary 

 ingredients for the production of the gas, and plunging the other extremity in a 

 freezing mixture. The gas, evolved in a closed space, speedily condensed into 

 a liquid state in the refrigerated extremity of the tube. In this way chlorine, 

 sulphurous acid, sulphuretted hydrogen, carbonic acid, protoxide of nitrogen, 

 cyanogen, ammonia, and hydrochloric acid were successively reduced to a liquid 

 state. With the exception of chlorine, all these liquefied gases were colorless 

 and perfectly transparent ; and all of them had a refractive power supenor to 

 that of water. The attempts made to reduce the other gases, especially hydro- 

 gen, oxygen, and nitrogen to a liquid state were fruitless. Twenty years later 

 (in 1844) Faraday resuminl these experiments by directly condensing the gases 

 by mechanical processes in very strong and hermetically sealed tubes, refrige- 

 rating them by means of the mixtme of ether with solid carbonic acid pro- 

 duced by Thiloriei-'s method. The condensation could be brought to fift\' 

 atmospheres, and the lowering of temperature to — 1C6°F., or 110°C. below 0°. 

 In this way Faiaday succeeded in liquefying, besides the gases which I have 

 already mentioned, olefiant gas, phosphuretted hydrogen, and arseniuretted 

 hydrogen, as also liuosilicic acid ; but he did not succeed in solidifying them. 

 On the other hand, by applying his new process to the gases which he had pre- 

 viously liquefied, he brought them not only to a liquid state, but even to that 

 of transparent and crystalline solids ; hydrochloric gas alone of these latter 

 would not become solid, whilst hydriodjc and h^'drobromic gas were successively 

 liquefied and solidified. 



It is easy to understand all the importance of an investigation tlie result of 

 which was to modify completely the received ideas as to the constitution of the 

 permanent gases by causing them to enter into the category of simple vapors ; 

 this was to intxoduc« into molecular ph3'sics a new and important notion, the 

 consequences of which have gradually unfolded themselves. 



It is also to a question of molecular physics that we must refer the memcjir 

 on the relations of gold and the other metals to light, published by Faraday in 

 1857. Among other interesting facts that this memoir contains, we shall cite 

 that of a leaf of beaten gold, which, wlien placed upon a plate of glass, 

 becomes perfectly transparent and colorless when it is brought to a high tem- 

 perature, and which, when seen by transmitted liglit, resumes its green color 

 when it is subjected to strong pressure. A great number of experiments upon 

 the pulverulent deposits of various metals obtained by electrical discharges 

 transmitted through very fine wires, led to remarkable results as to the varia- 

 tions of color arising from change in the molecular state of the same body. "We 

 also find in this memoir a detailed investigation of the various colors presented 

 by different solutions of gold, and especially of the fine raby-red tinge obtained 

 by the solution of a quantity of gold which, if agglomerated into a single mass, 

 would not occupy the seveu-hundre<l-thousaudth part of the volume of water 

 which it colors. It is not necessary to dwell upon the interest presented by 

 researches having for their object the study of the influence, still so imperfectly 

 known, of the molecular structure of bodies upon their relations to light, and 

 especially upon their transparency. 



Among the nmuerous works of Faraday relating to the .applications of sci- 

 ence to the arts, we shall confine om'selves to citing his researches u])on the 

 manufactm-e of steel, and of glass for optical jjiurposes, these being the most 

 important. 



It was by the analysis of the Indian steel called tcoofs that he was led, in 

 concert with Stodurt, to compose an alloy which had all the properties of this, 

 by combining aluminium with iron and carbon, hi a letter addressed in 1820 



