18 THE FAT OF MILK. 



and similarly two di-hydrins : thus 



CELC1 CH,C1 



CH(OH) and CHC1 

 CH 2 C1 CH 2 (OH) 



Both, compounds are simultaneously produced. 



By the action of alkalies on both the dichlor-hydrins, epichlor- 



CH 8 C1 

 hydrin CH \^ is produced. 



A mono-iod-hydrin also appears to be produced by the action 

 of hydriodic acid. 



The penta-chloride and penta-bromide of phosphorus produce 

 trichlor- and tribrom-hydrins, which are the a-/?-y-trichlor- and 

 a-/?-y-tribrom-derivatives of propane. 



Phosphorus tri-iodide or concentrated hydriodic acid produce 

 a mixture of allyl and iso-propyl iodides with propylene. 



By the action of dehydrating agents acrolein, acrylic aldehyde, 

 C 3 H 4 is formed. 



Glycerol is very soluble in water and alcohol, but insoluble in 

 ether and chloroform. 



Cholesterol, C^H^OH, is a mono-hydric alcohol, containing 

 one unsaturated bond. This is shown by its combination with 

 two atoms of bromine to form dibrom-cholesterol, C 26 H 43 Br 2 OH. 

 It is laevo -rotatory, having an [a] D 36-6 (Dragendorff) or 

 31-6 (Lindenmeyer). 



It is easily soluble in hot alcohol, crystallising out on cooling 

 in characteristic plates ; occasionally from alcohol and more 

 often from ether it is obtained in needles. 



Cholesteryl acetate, melting point 115-4, is obtained by the 

 action of acetic anhydride on cholesterol. The benzoate is 

 obtained by heating cholesterol with benzoic acid under pressure, 

 and melts at 150 to 151 C. 



Vegetable oils, which may be used as adulterants of butter, 

 contain phytosterol, the acetate of which has a much higher 

 melting point, and is thus detected. 



The most characteristic reaction is the following, due to Sal- 

 kowski : About 10 milligrammes of cholesterol are dissolved 

 in 2 c.c. of chloroform, and the solution shaken with an equal 

 measure of strong sulphuric acid in a corked test tube. The 

 chloroform layer becomes blood-red, passing to cherry-red and 

 purple, the last colour being permanent for several days. The 

 sulphuric acid acquires a well-marked green fluorescence. If the 

 test tube be not corked, or if the chloroform solution be poured 

 into a basin, the colour changes to blue, green, and, finally, yellow, 

 probably due to moisture. On addition of water the solution 



