ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 425 



steel, and the effect upon structure of the stresses set up by the volume 

 changes. The results of quenching and annealing experiments upon 

 seventeen steels, containing - 09 to 1*2 p.c. carbon, are given. To 

 avoid the laborious sectioning by grinding of quenched pieces, some of 

 the specimens were cut in t\fO before hardening, the cut faces were 

 polished and placed in contact, the pieces were fastened together with 

 wire, and the joint luted with sodium silicate. The compound piece was 

 readily divided after heating and quenching. The formation of an outer 

 ring of martensite, surrounding osmondite in which martensite particles 

 are embedded in the form of an inner ring, is explained. 



Iron-titanium Alloys.* — J. Lamort has studied the iron-titanium 

 system in the range to 24 p.c. titanium. Up to about 6 p.c. titanium 

 the alloys consisted of crystals of a solid solution ; beyond this concen- 

 tration a eutectic, increasing in amount with increasing titanium content, 

 was observed. At about 13 '2 p.c. titanium the alloy consisted wholly 

 of eutectic. A phase K, which is possibly the compound Fe 3 Ti, then 

 appeared, and increased, at the expense of the eutectic, with increasing 

 titanium content. The alloy, containing 21 "5 p.c. titanium, consisted 

 chiefly of K, and contained very little eutectic. The etching reagents 

 used were hydrochloric acid, concentrated and also in dilute alcoholic 

 solution, and hydrofluoric acid. The duplex character of the eutectic, 

 which consisted of the saturated solid solution and the phase K, is 

 clearly shown by the photomicrographs. Inclusions of rod or cube 

 form, yellow or reddish-yellow in colour, were numerous, and were 

 evident in polished unetched sections owing to their comparative hard- 

 ness. They were shown to be nitride or nitro-cyanide of titanium. The 

 structure of some samples of commercial f erro-titanium is described. 



The 4*3 p.c. Carbon Eutectic.j — J. E. Fletcher discusses the manu- 

 facture, properties, and structure of cast-iron. Commercial cast-irons 

 are regarded as modifications of the 4 ■ 3 p.c. carbon eutectic (white iron), 

 which may be considered as the natural form of pure cast-iron. The 

 modifications occur through the addition of silicon, manganese, or other 

 elements, or because of peculiarities in the processes of manufacture. 



Influence of Carbon and Silicon in Cast-iron.:}: — F. Wiist and 

 K. Kettenbach have determined the mechanical properties and studied 

 the microstructure of a large number of pure cast-irons containing vary- 

 ing amounts of carbon and silicon. Grey cast-iron may be regarded as 

 a carbon steel, the structure of which is mechanically interrupted by 

 graphite crystals. The mechanical properties of grey cast-iron are 

 essentially dependent upon the amount and form of the graphite. 

 Changes in carbon and silicon content influence the mechanical pro- 

 perties chiefly through their effect on the amount and form of the 

 graphite. Increase in carbon and silicon causes an increase in the size 

 of the graphite flakes. The best mechanical properties are obtained 

 when the graphite exists largely in the form of temper-carbon. 



* Ferrum, xi. (1914) pp. 225-34 (37 figs.). 



t Foundry Trade Journal, xvi. (1914) pp. 278-84 (13 figs.). 



X Ferrum, xi. (1913-14) pp. 51-4, 65-80 (20 figs.). 



Aug. 19th, 1914 2 f 



