28 DAIRY ANALYSIS 



While the substitution of the alkaline solution avoids 

 the objections to a strong acid, this method has the 

 drawback that the corks become slippery and tend to 

 come out of the bottles. 



Gravimetric Estimation of Fat. Of the numerous 

 methods for the estimation of fat, the Storch, the Ritt- 

 hausen, the Werner-Schmid, and the Gottlieb methods 

 all present advantages. 



The Storch Method. Place three or four grammes of 

 ignited kieselguhr in a basin, and pipette 10 c.c. of 

 milk in such a manner that it is all absorbed by the 

 kieselguhr ; dry on the water-bath with occasional 

 stirring to break up lumps, grind fine, and transfer to 

 a fat-free thimble, rinsing out the basin with fresh 

 quantities of kieselguhr ; place the thimble in a Soxhlet 

 extractor, rinse the basin, pestle, &c., with ether, and 

 pour this into the thimble ; extract the kieselguhr 

 with ether. 



The Ritthausen Method. See Estimation of Proteins, 



P- 34- 



The extraction in these methods is performed by 

 attaching a weighed flask to the bottom of the 

 extractor to receive the ether containing the fat, and 

 connecting the extractor to an upright condenser ; the 

 flask is immersed in water kept warm by a small flame, 

 and the ether continually distils up, is condensed, and 

 runs back into the extractor, from which it siphons 

 back into the flask when the extractor is full. 



The kieselguhr should be extracted about four hours, 

 and casein about one and a half hours, after which the 

 ether is distilled from the flask, and the fat freed from 

 ether by placing in a water-oven for twenty minutes, 

 blowing into and rotating the flask every five minutes. 

 After cooling for a quarter of an hour, the flask is 

 weighed, and the increase of weight represents the fat. 



It is advisable to return the flask to the water-oven 

 for a second period, and re-weigh to make sure that 

 all the solvent has been removed. The fat may be 

 melted and dissolved in petroleum ether which is 



