504 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The layer of cotton-wool prevents the entry of germs from without. 

 The apparatus is sterilised in the usual way (figs. 107-109). 



Fig. 108. 



Fig. 107. 



Fig. 109. 



Micro-Crystalline Structure of Platinum.* — T. Andrews obtained 

 a satisfactorily developed crystalline structure of a polished platinum 

 ingot after boiling it for 45 seconds in aqua regia composed of 4 parts 

 of hydrochloric acid (sp. gr. 1*2) to 1 part of nitric acid (sp. gr. 1*42). 

 The general micro-crystalline structure was observed to be allotrio- 

 morphic in character, and derived from a system of interfering cubes 

 and octahedra, the cubic and hexagonal forms being frequently notice- 

 able. The size of the large crystal grains varied from 0*002 in. to 

 0*04 in. in size, and the smaller crystals ranged from about 0*0002 in. 

 to about * 007 in. There were indications that the smaller crystals 



* Proc. Roy. Soc, lxix. (1902) pp. 433-5 (1 pi. of 6 photos). 



