ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 739 



to have been overlooked. Ft was found to be valuable In determining 

 the presence of zinc in certain marine Gastropods, and by its means zinc 

 was detected readily in the blood of these .Molluscs in a few minutes, 

 while the tests in ordinary use require many hours and much material. 

 In the solutions of tissue ash used the copper was first removed by 

 means of H 2 S, and the filtrate concentrated to a small bulk. A drop of 

 this solution was then placed on a Microscope slide and digested with a 

 drop of freshly prepared nitro-prusside solution. On cooling, the rect- 

 angular plates and prisms of the zinc salt were deposited. 



Gelatin Mass for Fixing and Mending Bone Preparations.* — 

 C. Skoda has found that the following mixture makes an excellent fixa- 

 tive and reparative for uniting and repairing bones intended for museum 

 and demonstration purposes. The adhesive consists of isinglass 2*0, 

 white dextrin 1 •(), zinc oxide 0*1. 



It is not advisable to make more than is necessary, as the mass does 

 not keep well. It may be thinned by dilution with water if necessary, 

 e.g. it requires to be thin for fixing a weasel's tooth in the jaw and 

 thick for a lion's. 



Hardening of Organs with Formalin. f — V. L. Neumayer hardens 

 brain and other organs by means of formalin, and obviates the disagree- 

 able vapour with ammonia. The method is chiefly intended for brain, 

 which is immersed for about three weeks in 10 p.c. formalin. The 

 viscus is then placed for eight days in 12*5 p.c. ammonia, after which 

 it is soaked in strong hydrochloric acid, diluted ten times, from eight 

 to fourteen days ; usually eight are sufficient. 



Instead of hydrochloric, nitric acid diluted five times may be used. 



It is advisable to test the acid solution from time to time, and renew 

 it if the acidity be diminished or lost. 



Metallography, etc. 



Questions in the Chemistry of Iron.J — H. von Jiiptner deals with 

 the physical chemistry of the alloys of iron, considering the iron-carbon 

 system somewhat fully. The general theory of the solidification of 

 solutions and alloys is outlined. Pure iron may exist in at least four 

 modifications : above 1550° C. liquid, 1550°-900° y, 900°-760° /?, 

 below 760° a. Liquid iron is capable of holding 4*3 p.c. carbon in 

 solution at 1186°, more at higher temperatures : y-iron dissolves ■ 95 p.c. 

 at 700° to 2 p.c. at 1186° ; /3-iron appears to dissolve about - 15 p.c. at 

 760° ; while carbon is nearly if not quite insoluble in a-iron. It is 

 found that on dissolving pig-iron, steel, etc., in dilute nitric acid, the 

 power of the combined carbon to colour the solution varies greatly in 

 different cases. These facts, together with others, lead to the conclusion 

 that there are four varieties of combined carbon : Fe 3 C, Fe 2 C, hardening 

 carbon in annealed steel, and hardening carbon in hardened steel. The 

 conditions of equilibrium between Fe and Fe 3 C, Fe and Fe 2 C, Fe and C, 



* Auat. Anzeig., xxix. (1906) pp. 380-2. t Tom. cit., pp. 378-9. 



X Ber. Deutsch. Chem. Ges., xxxix. (190G) pp. 2376-2402 (15 figs., 7 photo- 

 micrographs). 



