HANDBOOK FOR BIO-CHEMICAL LABORATORY. 



filtered, evaporated to dryness with magnesium carbonate, and 

 the residue extracted with alcohol. Exhaust the part insol- 

 uble therein with hot water, filter, and evaporate the filtrate 

 to a syrupy consistency, and allow to stand in a cool place un- 

 til the lactose crystallizes out. If the syrup is at all colored, 

 the solution must be decolorized by passing the solution 

 through animal charcoal. 



Properties. Lactose crystallizes in rhombic prisms which 

 contain a molecule of water of crystallization. It is soluble 

 in 6 parts cold and 2.5 parts hot water. It has only a faint 

 s \veut taste. It is insoluble in ether or absolute alcohol. 

 Aqueous solutions are dextro-rotatory, (a) D -f- 52.5. 

 Milk-sugar combines with bases ; the alkali combinations are 

 insoluble in alcohol. Solutions of lactose reduce Fehling's 

 solution, but less powerfully than dextrose. On warming 

 with phenyl-hydrazine acetate it gives on cooling a yellow 

 precipitate of phenyl-lactosazon, C 24 H 32 N 4 9 . By boiling 

 with water, or more readily on boiling with acids, or by 

 means of inverting ferments, as in the alimentary canal, it 

 takes up water and is converted into a glucose called galac- 

 tose. It undergoes alcoholic fermentation by the action of 

 certain schizomycetes, producing lactic acid at the same time. 



Maltose, C 12 H, 2 U + H 3 0. 



Preparation. 500 grms. potato-starch are thoroughly 

 mixed with 2.5 litres cold water and converted to a paste by 

 heating on the water-bath. Allow this paste to cool to 

 60-65 C., and add a watery extract of 30-35 grms. of air-dried 

 malt made at 40 C. Keep at 60 C. for an hour, then boil, 

 filter, and evaporate to syrup in a flat porcelain dish. This 

 is extracted several times with boiling 90$ alcohol. If no 

 crystals of pure maltose are at your disposal, boil a portion of 

 the syrup with absolute alcohol, filter, evaporate to thin syrup, 

 and allow it to stand in thill layers until it crystallizes, which 



