652 



SUMMARY OF CURRENT RESEARCHES. 



emulsion is calculated from the known size of the loop, the cover- 

 glass, and the field of vision. The complete details of this method are 

 promised later. 



Fig. 182. 



Fig. 183. 



Fig. 184. 



& 



=s 



Method of Identifying Butter.* — Mr. J. A. Hummel made an ex- 

 amination of Brown and Taylor's official method of identifying butter. 

 In the manufacture of renovated butter, the butter fat is melted and then 

 rapidly cooled in a stream of cold water ; this induces a semi-crystallisa- 

 tion of the fat which may be recognised by the Microscope. A small 

 piece of the sample is placed on a glass slide and pressed into a thin 

 fiim with a cover-glass ; it is then at once examined with a polarising 

 Microscope magnifying 120-150 diameters. A selenite plate is placed 

 between the slide and the lower Nicol's prism. In every case normal 

 butters gave a uniform blue-coloured field, showing the entire absence 

 of crystals ; but the renovated samples gave a blue field mottled witli 

 yellow, which varied in intensity, but was very distinct in each case. 



Stine, W. M. — The Microscopic Study of Metals. 



[An interesting introduction to the subject] 



Journ. of App. Micr., March 1900, pp. 786-91 (2 figs.). 

 Chasiot, E. M. — Micro-chemical Analysis. 



[A series of introductory articles.] Journ. of App. Micr., Jan. et seq. 1900. 



* Journ. Amer. Chem. Soc, xxii. (1900) pp. 327-9. See Journ. Chem. Sot-., 

 lxxviii. (1900) Abstr. ii. p. 582. 



