CHEMICAL SCIENCE. 185 



of pulverized gypsum, and pour over it half an ounce of the milk to 

 be examined. As soon as this mixture becomes warm, the milk is de- 

 composed, when the butter and cheese attach themselves to the gyp- 

 sum, so that we can let it boil freely without danger of losing any 

 portion of the solid substances. When the contents of the saucer 

 have reached a doughy consistency, which occurs in fifteen minutes, 

 the heat must be diminished. The paste should then be dried, a 

 vapor-bath being the best way, when it is soon changed into a grained 

 powder; having ascertained by weighing, at short intervals, that 

 the water has disappeared, we find the proportion of solid ele- 

 ments in the milk by noting the difference in weight between the 

 saucer now, and when empty. If we desire to find also the quantity 

 of fatty matter which is contained in the solid residuum, we have 

 only to extract the powder in it by means of sulphuric ether, and the 

 loss of weight thus occasioned gives the quantity of fat which is con- 

 tained in the milk. On an average, pure milk contains from 10 to 12 

 per cent, of fatty matter, though this is often reduced one half by adul- 

 teration." Condensed from the Patent-Office Report for 1848. 



IMPROVED METHOD OF PRESERVING MILK. 



THE following improved method of preserving milk has been dis- 

 covered and patented by M. F. H. Louis. The milk is to be mixed 

 with well-clarified raw sugar, four ounces to the gallon. It is then to 

 be evaporated with agitation. When nearly solid, it must be pressed 

 into cakes of suitable size. Steam may be used for the evapora- 

 tion ; or, if time is no object, spontaneous evaporation in very shal- 

 low pans, with the fluid not more than one tenth of an inch in depth, 

 or a drying chamber may be used, the temperature not to exceed 122 

 Fahr. The cakes remain sweet and fresh for a long time, and are 

 soluble in warm water. Another process is, to heat the sweetened 

 milk nearly to the boiling point, and before it becomes cold, to curdle 

 it by rennet or a weak acid. The curd is separated from the whey, 

 and by strong pressure, after washing in cold water, it is obtained free 

 from adhering water. The whey is to be evaporated to dryness. The 

 curd, placed over a slow fire, is continually stirred, and the dried 

 whey added very gradually, with a small portion of bicarbonate of 

 soda. After a while, the ingredients melt and unite. A small quan- 

 tity of finely pulverized gum dragon hastens the solidification. Cream 

 may be preserved by the same methods. Chemical Gazette. 



ADULTERATION OF PORT "WINE. 



THE Westminster Review for October contains some extracts from 

 a recent pamphlet, entitled " A Word or Two on Port Wine." 



The author of the pamphlet in question, Mr. Joseph James For- 

 rester, thus explains his object in its publication : The qualities of 

 port wine most prized have been different at different periods. Some- 

 times dryness and astringency, sometimes fruitiness and smoothness, 

 at one time, great delicacy, and at another, fulness, have been sought 



16* 



