RECENT ADVANCES IN SCIENCE 473 



trichroitic crystals a displacement of the maximum corre- 

 sponding to the water molecule was experienced, using polarised 

 light, according to the direction of the light beam in relation 

 to the optical axis or axes of the crystal. The " hydrate " 

 water paralleled in behaviour the specific optical characteristic 

 of the crystal and was therefore anisotropic in optically aniso- 

 tropic crystals. The hydrate molecules assume the symmetry 

 of the crystals which house them. As might be expected also, 

 the uncombined water maximum at 3*2 fi is in general shifted 

 when the water becomes " hydration " water. 



Corrosion. — The complicated and costly phenomenon of the 

 sea-water corrosion of ship condenser tubes has been engaging 

 the attention of scientists for some considerable time. The 

 three years' work of the Corrosion Committee has advanced 

 our knowledge very considerably on this highly important 

 subject. At a recent meeting of the Faraday Society the 

 subject was under discussion and the conflicting views were 

 debated. It is highly satisfactory to record that the matter 

 has now been definitely taken up by the Government, who are 

 establishing an experimental station at Southwick and financing 

 the future investigations. 



Some of the results so far obtained under the Committee are 

 published in a paper by Gibbs (Trans. Faraday Soc. 1916, 11, 

 258). Gibbs shows that the rate of corrosion progressively 

 diminishes as copper is alloyed with zinc until an alloy corre- 

 sponding with the formula CuZn is obtained. This alloy is 

 not attacked at ordinary temperatures by sea water. 



With ordinary 70 : 30 brass there is an initial minimal 

 corrosion rate which soon disappears. Rising temperature up 

 to 50 C. increases the rate of corrosion, which then diminishes 

 quickly. The point of attack is initially towards copper, then 

 general, and finally towards zinc. The intermediate formation 

 of oxy chloride seems to be a definite determinant of reaction. 

 Hard-drawn tubes have a greater resistance to corrosion than 

 annealed alloys, but in the former the dezincification is greater. 



Polymorphism. — Some careful experiments on the transition 

 points of the polymorphic forms of pure iron are recorded in a 

 paper by Ruer and Goerens (Ferrum, 191 5, 13, 1). The iron 

 was electrolytically prepared almost free from carbon. It 

 gave a freezing point at 1528 with transition points a — /3 at 

 769 , £ — 7, 906 , and 7 — 8 at 1401 . They failed to confirm a 

 3i 



