COMPOSITION AND PROPERTIES OF CASEIN. 37 



insulating materials known for electrical purposes. These 

 qualities are sufficient to secure for galalith a very extensive 

 sphere of application, certain to react favourably on the milk 

 industry. 



Already this material is used for manufacturing a large 

 number of articles, such as plates, combs, cigar-holders, 

 fittings, etc. ; and it is also possible to utilise galalith for 

 accomplishing new technical results. 



When a solution of casein is tVeated with formaldehyde 

 and poured on to glass plates it furnishes transparent films, 

 insoluble in water. Spitteler and Krische found that the ad- 

 dition of formaldehyde to casein solutions gave, on subse- 

 quent precipitation, products that swelled up in water and 

 had a fracture like cartilage. On the other hand, they dis- 

 covered that this drawback could be remedied by treating the 

 casein with formaldehyde after precipitation by acids or lead 

 acetate, preferably after the precipitate had been freed from 

 water, as far as possible, by evaporation or pressure, the 

 hardening with formaldehyde being then undertaken. The 

 treatment gives products with the properties of horn. In 

 their patent specification the inventors give a comparative 

 table of the behaviour of buffalo horn and of casein products 

 prepared in various ways, showing that while buffalo horn 

 absorbs 15^ to 18 per cent, of water, when submerged in that 

 liquid for thirty-three days, the new product hardened with 

 formaldehyde takes up 16 to 23 per cent, of water, and there- 

 fore behaves in a very similar manner. 



The determination of casein is performed by precipitating 

 the milk with magnesium sulphate (solid and in solution), 

 the nitrogen in the precipitate being determined, and the 

 casein calculated from the result. The filtrate from the 

 casein precipitate is diluted, and the lactalbumen thrown 

 down with tannic acid or phospho-tungstic acid, the nitrogen 

 in this precipitate being also determined. 



