138 MILK AND DAIRY PRODUCTS PART 



2. Rose-Gottlieb Method. 



This method, which was originally designed for the estimation 

 of fat in milk, and is described on p. 52, can be used with 

 advantage also for the determination of fat in butter. 



According to A. Hesse, 1 about 2 g. of butter are weighed out 

 into a 3 cm. long, half-cylindrical glass tube, or simply wrapped 

 in a piece of stiff fat-free paper of the same form. The tube or 

 paper and the contained fat are then introduced into a Gottlieb 

 cylinder, and hot water added until the 10 cm. mark is reached. 

 If the butter does not melt, the cylinder is placed in warm 

 water until it does. Then 1 c.c. of ammonia and 10 c.c. of 95 per 

 cent, alcohol are added exactly as in the estimation of milk fat. 

 If the mixture is still warm, the cylinder is cooled down in cold 

 water so that the ether which is to be added will not evaporate 

 so quickly. The cooling must not, however, be carried too far, 

 otherwise the butter will become solid again. Twenty-five c.c. 

 of ether are then added, the contents of the cylinder mixed by 

 repeatedly inverting it, and afterwards 25 c.c. of petroleum ether 

 are added and the mixing repeated. 



After the different layers have separated quite sharply 

 from one another, the clear ether-fat solution is siphoned off in 

 the usual way, the lower opaque layer not being disturbed. 

 Then 50 c.c. of ether are poured into the cylinder and at 

 once siphoned off without being mixed with the other liquid. 

 Finally, the residual liquid is shaken with a mixture of 25 c.c. 

 ether and 25 c.c. petroleum ether, and, after settling, the 

 ethereal layer is drawn off. The three lots of ether are 

 naturally all placed in the same tared flask, which is weighed 

 again after the ether has been evaporated and the fat dried. 



These repeated extractions with ether and petroleum ether 

 are necessary if exact results are to be got. If the above 

 directions are carefully followed, the results will be found to be 

 in very close agreement with those obtained from the extraction 

 method. Thus the Rose-Gottlieb method is easier and more 

 convenient, and also considerably quicker than the extraction 

 method. 



1 Molkerei-Zeitung, Hildesheim, 1903, No. 27. 



