PRESERVATION OF FOOD. 189 



Testing Butter for Casein. — Add ether to the butter, con- 

 tained in a flask, and shake them together for some time. 

 The butter is dissolved and the cassein remains. (Archiv. 

 der Pharm. Ivi.) 



3. Preservation of Food. — This subject has also been but 

 superficially investigated bj the chemist. Some of the sub- 

 stances used for preserving food are ice, sugar, alcohol, and 

 vinegar ; but more attention should be given to the preserva- 

 tion of food, by procuring it in a dry state, where chemical 

 action cannot take place. We offer the preservation of milk 

 as an example. 



Ice. — As this article is now regarded as almost indispensable 

 to health in summer, and as it is unquestionably one of the 

 greatest luxuries, it would be desirable to manufacture it in 

 the season when it is wanted, especially in latitudes and lo- 

 calities where it is not obtained in sufficient quantity in winter 

 and cannot be procured at a moderate cost by importation. 

 Several of the freezing mixtures, formerly used as subjects 

 of pleasing experiment by the chemist, begin to attract atten- 

 tion, as means of economic manufacture of ice in summer. 

 See an article on the subject, in Amer. Journ. 2d ser. vii. 280. 



Preservation of Milk. — Louis (Ch. Gaz. vii. 48) renders 

 milk portable without impairing its original sweetness, by 

 mixing it with clarified sugar, 4 oz. to the gallon, evaporating 

 it in shallow pans by steam, and removing it at the solidifying 

 point, and pressing it into cakes. 



Another method recommended is to curdle the sweetened 

 milk by rennet, and then to separate the solid from the liquid 

 portion, by means of a sieve. The whey is evaporated to dry- 

 ness and the residue mixed, by the aid of heat and a little 

 bicarbonate of soda (1 pt. to 20 pts. of residue), with the 

 curd previously washed and pressed. When the amalgamation 

 is perfect, sufficient tragacanth is added to promote the solidi- 

 fication of the mass. 



3Iilk and Cream. — Bethel has obtained a patent (Newton's 

 Journal, 1849) for preserving milk or cream, by first scalding 

 it, and then surcharging it with carbonic acid by means of 



