LECTURE XVI.] HISTORY OF CHEMISTRY. 343 



phosphorus, etc.) in air or oxygen at high temperatures, for the 

 purpose of attaining still higher temperatures ; as, for example, 

 in the blast furnace, or in the ingenious Bessemer process. 

 The development of these methods by Goldschmidt, 50 and 

 their application to the production of metals such as chromium, 

 manganese, iron, and nickel, free from carbon, and of a large 

 number of alloys, are new however. 



1 must here recall the interesting results obtained, partly by 

 Victor Meyer 51 and partly by Crafts, 52 by the application 

 of the method of vapour density determination devised by 

 the former. 53 I regard as worthy of mention the proof that 

 the molecule of iodine, I 2 , breaks up at high temperatures into 

 single atoms ; 54 and also the facts that the beginning, at least, 

 of a similar dissociation has been ascertained in the case of 

 bromine; 55 that the molecule of arsenic, As 4 , similarly splits 

 into two; that potassium iodide even at high temperatures 

 corresponds to the formula KI, and cuprous chloride to the 

 formula Cu. 2 Cl. 2 , etc. 



If the attainment of high temperatures has thus been of 

 service for the purposes of our science and of technology, so 

 likewise the endeavours, on the other hand, to obtain low 

 temperatures have led to great advances, and to results of 

 altogether unforeseen importance. In the preceding lecture 

 (p. 322), where the inter-relations of the states of physical 

 aggregation and the significance of the critical temperature are 

 referred to, the results of Pictet, of Cailletet, and of Wroblewsky 

 on the liquefaction of the so-called permanent gases are stated. 

 Of especial importance were the detailed investigations of 

 Wroblewsky and Olszewsky, who first obtained quantities of 

 oxygen and nitrogen in the liquid state, and particularly de- 

 scribed many of their properties. 5 " The mode of measuring 



50 Annalen. 301, 19; Z. f. Elektrochemie, 1897-98, Heft 21. B1 Be- 

 richte. 13, 1010. 52 Comptes Rendus. 90, 183 ; 92, 39 ; Berichte. 13, 

 851. 5:i Berichte. II, 1867 and 1946 ; 12, 609 and 681 ; etc. 54 Comptes 

 Rendus. 90, 183 ; 92, 39 ; Berichte. 13, 851. 55 Langes and Victor Meyer, 

 Fyrochemische Untersuchungen, Braunschweig 1885. r ' 6 Wiedem. Ann. 20, 

 243 and 860; Wien. Akad. Ber. 1885, 91 (2), 667 ; Monatshefte. 9, 1067. 



