ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 429 



sisfcing of potassium bichromate 40 grm., sulphuric acid (sp. gr. 1 • 84) 

 1 c.cm., water 100 c.cm., until a slight attack is visible to the naked 

 eye ; then rinse in water and immerse in a dilute acid ferric-chloride 

 solution till a faint coloured film is seen to cover specimen ; withdraw at 

 once, wash with water, and dry with alcohol. 



Use of Titanium in Steel-making.*^An exposition, accompanied 

 by microphotographs, of the use and value of titanium as a deoxidiser 

 and cleanser in removing harmful occluded gases and slags in steel- 

 making is given by W. A. Janssen. It is added to the steel in the form 

 of ferro-titanium, and is usually employed to augment the deoxidation 

 begun by additions of ferro-silicon or ferro-manganese. Besides having 

 a high affinity for oxygen, titanium has the additional advantages over 

 other deoxidisers in the fusibility of the titanic oxide formed, also in the 

 fact that it readily combines with nitrogen at 800° C. to form a stable 

 nitride, which usually rises into the slag. Microscopical examination 

 sometimes reveals the presence of titanium nitride in steel as tiny, 

 hard, pink crystals, which, however, are less harmful than occluded 

 nitrogen. Titanium does not alloy wath steel ; the results of many 

 analyses of titanium-treated steels never showed a titanium-content 

 higher than 0'025 p.c. 



Bibliography of Alloy Systems.f— A complete list, with literature 

 references, of all binary, ternary, and quaternary alloy systems whose 

 equilibra have been investigated by microscopical, thermal or other 

 means, up to January 1917, has been prepared by C. Estes. The list 

 includes practically all the binary systems of the common metals, and a 

 large number of the rarer metals — -about sixty ternary and several 

 quaternary systems. A bibliography of investigations into the allotropic 

 modifications of metals is also added. 



Determination of Grain-size of Annealed Brass. | — The standardiza- 

 tion of grain-size is recommended by (i. A. Miller for controlling the 

 quality of annealed brass obtained from different sources. He describes 

 a method of measurement by comparison with a series of ten care- 

 fully prepared standard photomicrographs varying in grain-size from 

 0*025 mm. to 0-180 mm. These standards are prepared by counting 

 the grains within a definite area on a clear print, averaging the counts 

 of five different ol)servers. The comparison is effected most speedily 

 and accurately by throwing the image of the structure to be measured 

 on the ground-glass screen of the photomicrographic apparatus, and com- 

 paring with equally illuminated lantern-slides of the standards, placed 

 in a frame also attached to the photomicrographic apparatus. Check- 

 measurements by difi^erent observers made thus did not vary by more 

 than • 005 mm. 



* Foundry, xlv. (1917) No. 293, pp. 15-19 (9 figs.). 



t Met. and Chem. Engineering, xvi. (1917) No. 5, pp. 273-82. 



I Met. and Chem. Engineering, xvi. (1917) No. 7, pp. 378-80 (2 figs.). 



