374 OTHER MILK PRODUCTS. 



The earlier methods of cheese analysis consisted of the esti- 

 mation of water, by drying at 100° C. (212° F.) to constant 

 weight ; of fat, by extracting with ether ; of ash, by ignition ; 

 and of casein, by difference ; this method has the advantage of 

 simplicity, but gives no information as to the changes that have 

 taken place during ripening. 



The following method will give fair results, and is easy of 

 execution : — 



Richmond's Method — Water, Fat, and Ash. — Three to 

 five grammes of cheese are weighed into a wide platinum dish 

 and dried in the water-oven till the fat begins to run away from 

 the cheese. The basin is then turned up, so that the fat collects 

 at one side, and the drying continued for an hour or so. It 

 frequently happens that no fat runs away from the cheese ; in 

 this case the turning up of the basin may be dispensed with. 

 The basin is then removed from the oven, and treated several 

 times with ether to remove the fat. The ethereal solution is 

 collected in a flask, the ether evaporated, and the fat dried and. 

 weighed. The basin and its contents are replaced in the water- 

 oven, and the residue dried to constant weight. The combined 

 weight of the fat and residue subtracted from the original weight 

 gives the water. It will be found that the removal of the fat 

 facilitates drying, but it is difficult to remove the whole of the 

 fat in this manner. The residue may now be incinerated at a 

 low red heat, and the ash weighed ; in this the salt may be 

 estimated by solution in water, and titration with silver nitrate 

 solution, using potassium chromate as indicator. 



It is advisable to make a separate estimation of the fat. This 

 may be done by Short's method, which consists in grinding up a 

 few grammes of cheese with twice its weight of anhydrous copper 

 sulphate, and extracting the mixture with ether in a Soxhlet 

 extractor. Schleicher and SchuU's thimbles are very convenient 

 for holding the mixture. The Werner-Schmidt method is also 

 applicable. To 2 or 3 grammes of cheese 5 c.c. of water and 

 10 c.c. of strong hydrochloric acid are added, and the whole 

 boiled with constant shaking till all, except fat, is dissolved. 

 The solution is cooled, about 25 c.c. of ether added, and the tube 

 well shaken. After complete separation, as much as possible 

 of the ether is drawn off, and a fresh portion added. After 

 four or five repetitions of the same process, the extraction of fat 

 is complete. The combined ether extracts are then evaporated, 

 and the fat weighed. 



M. Weibull uses the Gottlieb method as follows : — 2 to 3 

 grammes of cheese are placed in a graduated tube, heated with 

 10 c.c. of ammonia to 75° C. with frequent shaking ; if the cheese 

 is not all dissolved by this treatment 10 c.c. of alcohol is added. 



