Penta-aCetylglucose and a-acetobromoglucose

Powdered anhydrous d-glucose (25 g.) is mixed in a mortar with anhydrous sodium acetate (12 g.) and the mixture is then heated in a half-litre round-bottomed flask on the water bath (with frequent shaking) with pure acetic anhydride (125 g.), so that after about half an hour a clear solution forms. After two hours more the solution is poured in a thin stream, with stirring, into a litre of ice-water. The crystalline mass which separates is powdered as carefully as may be, and after some hours, when most of the excess of acetic anhydride is decomposed, is collected at the pump and then kept for a few hours longer under water. Finally it is again collected at the pump, pressed down well, and recrystallised from about 120 c.c. of alcohol. The penta-acetyglucose so obtained is sufficiently pure for further use. Yield 35-40 g. 

Acetobromoglucose.—Glacial acetic acid is saturated at 0° with hydrogen bromide2 and 50 g. of the solution are poured on to 25 g. 

2 Preparation of Hydrogen Bromide.—Red phosphorus (6 g.) is mixed to a sludge with 15 c.c. of water in a distilling flask (capacity 250 c.c.) having the side tube attached high up on the neck. The flask is connected to a U-tube containing 

Whole milk (2 litres) is diluted with an equal volume of water at 30°-40° and commercial rennet (0-1 g.), dissolved in a few cubic centimetres of water, is added. The mixture is then left at the same temperature until separation of the casein is complete (about two hours). The whey is filtered through a filter cloth, and after the liquid has run off the residue is pressed down well. The casein, which contains a great deal of fat, is ground in a mortar with a little 1 per cent sodium hydroxide solution 1 to 1-5 litres of sodium hydroxide solution of the same concentration are then poured on to the resulting paste, and the mixture is gently warmed in a porcelain basin until all but the fat dissolves. 

When the mixture stands over night in a filter jar the milk fat collects at the surface and can be separated cleanly at the pump. The filtrate is combined with the rest of the casein solution and the substance is again precipitated by the addition of 10-20 c.c. of glacial acetic acid. Finally the precipitate is collected by filtration 

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