360 



MILK. 



animal charcoal, yields us by filtration and 

 evaporation pure crystals of aposepedine. This 

 substance has the following properties : it is 

 somewhat bitter to the taste, very slightly so- 

 luble in alcohol, soluble in water, and of 

 greater specific gravity than that fluid. It sub- 

 limes when heated strongly, but always un- 

 dergoes a partial decomposition. It contains 

 sulphur. In addition to aposepedine, cheese 

 when decomposing has been found to contain 

 acetic acid, acetates of ammonia and potassa, 

 chloride of potassium, ammoniaco-phosphate 

 of soda, margarate and phosphate of lime, and 

 a peculiar extractive matter. 



I shall now proceed to consider the sugar of 

 milk which is left in the whey after the sepa- 

 ration of the cheese by rennet, and exists in 

 solution with the salts of the milk, lactic acid, 

 and animal extractive matter. 



Sugar of milk may be obtained from whey 

 by evaporating it to the consistence of a syrup, 

 and setting it aside for a length of time, when 

 small granular crystals of the principle are 

 observed to deposit. The following are the 

 principal qualities of sugar of milk. It has a 

 sweetish taste, the grains crushing with dif- 

 ficulty between the teeth ; its specific gravity 

 is 1.543. It contains about 12 per cent, of 

 water, which may be separated by carefully 

 fusing it ; when fused it is still quite white if 

 the heat be not too strongly urged. It is solu- 

 ble with difficulty in water, requiring three 

 parts of boiling water and six of cold for that 

 purpose. It is very slightly soluble in alcohol, 

 and quite insoluble in ether. When acted on 

 by concentrated nitric acid it becomes trans- 

 formed into a mixture of oxalic, malic, and 

 muric acids. By the action of caustic potassa 

 it is changed to a brown-coloured bitter mass, 

 which is insoluble in alcohol. 



Sugar of milk has been stated to be in- 

 capable of undergoing the alcoholic fermen- 

 tation; but late experiments by Hess (Poggen- 

 dorff, Annalen der Physick) shew that such 

 will occur, and an intoxicating liquor has been 

 long known among the Tartars, which is pre- 

 pared from the milk of the mare, and to which 

 they give the name of Koumiss. Sugar of 

 milk has been analysed by Berzehus: including 

 its 12 per cent, of water, its composition is as 

 follows : 



Carbon.... 40.125 or 1 atom, 

 Hydrogen . . 6.762 or 2 atoms, 



Oxygen 53.113 or 1 atom: 



or deducting the 12 per cent, of water, 

 Carbon.... 45.94 or 5 atoms, 

 Hydrogen . . 6 00 or 8 atoms, 

 Oxygen. . . . 48.06 or 4 atoms. 



It will be observed, on comparing the ana- 

 lysis of hydrous sugar of milk with that of 

 starch, that they accord very nearly, and sugar 

 of milk is convertible, as is the case with starch, 

 into true sugar, by the action of sulphuric acid ; 

 these facts strongly point out the curious ap- 

 proach to vegetable matter which is made by 

 this constituent of an animal secretion. 



After the crystallization of the sugar of milk 

 from the whey, we have left in solution, accord- 

 ing to the experiments of Berzelius, lactic acid 



and lactates, chloride of potassium, an alkaline 

 phosphate, phosphates of lime and magnesia, 

 and traces of oxide of iron. 



I shall not here enter upon the question 

 whether or not lactic acid be the peculiar acid 

 of milk, or whether the substance receiving 

 that name be only a modification of the acetic ; 

 the matter is to be found noticed at length in 

 the 7th volume of the French edition of Ber- 

 zelius' Chemistry. For my own part I can 

 only wish that one quarter of the animal acids 

 mentioned in our modern chemical works had 

 the same right to be distinguished as peculiar 

 animal principles. Mons. Lassaigne, in his 

 work bearing date 1836, when speaking of 

 lactic acid, says, " regarde pendant long temps 

 comme de 1'acide acetique modifie par une 

 matiere organique, M. Berzelius a titabli d'une 

 maniere incontestable sa veritable nature." 

 Anhydrous lactic acid has the following ulti- 

 mate composition. 



Carbon 50.50 



Hydrogen 3.60 



Oxygen 43.90 



Berzelius' analysis of skimmed cow's milk is 

 as follows : 



Caseous matter with some butter 2.600 



Sugar of milk 3.500 



Extractive, lactic acid, and lactates 0.600 



Chloride of potassium 0.170 



Alkaline phosphate 0.025 



Earthy phosphates, trace of oxide 



of iron 0.220 



Water 92.875 



The cream from this milk yielded the follow- 

 ing result : 



Butter 4.5 



Caseous matter 3.5 



Whey 92.0 



The specific gravity of this milk was 1.0348, 

 and that of the cream 1.0244. 



A specimen of cow's milk which I lately 

 examined was of sp. grav. 1.0338, and its solid 

 contents 121.85 in 1000 parts. 



The ashes of cow's milk, according to Pfaff 

 and Schwartz, are composed of phosphates of 

 lime, magnesia, and iron, phosphate of soda, 

 chloride of potassium, and soda, which, before 

 incineration, had existed in combination with 

 lactic acid. They found 1000 parts of the 

 milk yielded 3.742 parts of ash. 



According to the experiments of Van Stip- 

 trian, Luiscius, and Bondt, the proportion of 

 cream which separates from cow's milk is 

 about 4 per cent, of its weight. They ob- 

 tained from milk 2.68 per cent, of butter, 8.95 

 of casein, and 3.60 per cent, of sugar of milk. 

 The first milk which is observed in the breast 

 after parturition has received the name of colos- 

 trum ; it differs somewhat from ordinary milk. 

 It has been stated by some authorities that 

 scarcely any cream can be obtained from the 

 colostrum, and that no butter can be obtained 

 by churning. According to Stiptrian, Luiscius, 

 and Bondt, however, the colostrum from the 

 cow yields 11.7 per cent, of cream, 3 of butter, 

 and 18.75 of cheese. They state the specific 

 gravity of the colostrum at 1.072; dried and in- 

 cinerated it yielded 5^ per cent, of ash. They 



