530 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Xanthophyll and Carotin. 



These compounds are obtained as bye-products in the preparation oi 

 pure chlorophyll and in the preparation of the chlorophyllides. 



Xanthophyll. 



Xanthophyll is contained in the methyl alcoholic washings of the petroleum 

 ether (p 524). They are mixed with 4-5 litres of ether and diluted with water. 

 The ethereal solution is shaken with 30-50 c.c. of concentrated methyl 

 alcoholic potash to saponify chlorophyll b which is also present ; the chloro- 

 phyllin is removed by shaking the solution with water. The ethereal solution 

 containing the xanthophyll is dried with sodium sulphate, evaporated to 30 

 c.c. and mixed with 200-300 c.c. of methyl alcohol. By further evaporation 

 the ether is removed and the hot filtered methyl alcoholic solution deposits 

 crystals of xanthophyll on cooling ; if a small quantity of water be added the 

 separation is complete. The yield is 0*8 gm. from 2 kilos, of dried leaf. 



Carotin. 



Carotin is contained in the petrol ether filtrate from chlorophyll (p. 525). It 

 is concentrated in vacua at 40 to a small volume and the oily residue is mixed 

 with 300 c.c. of 95 per cent, alcohol. Carotin immediately begins to separate 

 in crystals, the separation becoming- complete on standing. A colourless 

 impurity which also separates is dissolved by adding 200-300 c.c. of petrol 

 ether and immediately filtering off the carotin, which is washed with a mixture 

 of 2 volumes of petrol ether and i volume of ether. The yield is 0^25 

 gm. from 2 kilos, of leaves. 



Xanthophyll and Carotin. 



These pigments are contained together in the ether and petrol ether 

 washings of the chlorophyllides. The washings are shaken with 30 c.c. of 

 concentrated methyl alcoholic potash to saponify the chlorophyll. This may 

 be repeated. The solution is diluted with water so as to obtain a yellow 

 ethereal solution and a green alkaline solution of the chlorophyllin salt. The 

 alkaline solution is extracted twice with ether. 



The xanthophyll and carotin are separated by partition between petrol 

 ether and methyl alcohol. The solution is shaken twice with i litre of 85 

 per cent, methyl alcohol, four times with 90 per cent, methyl alcohol. The 

 pigment is transferred to ether which occupies a volume of 2-5 litres. 



The xanthophyll in ether and the carotin in petrol ether are washed and 

 the solutions evaporated, finally in vacuo at 40. The xanthophyll is pre- 

 cipitated by adding i litre of petrol ether and filtered off on talc at o. It 

 is dissolved in i litre of ether, the solution is concentrated and diluted with 

 methyl alcohol and the ether evaporated. If xanthophyll separates, it is re- 

 dissolved by warming with the addition of more methyl alcohol. On cooling 

 the xanthophyll crystallises out. The yield is about i gm. and 0-3 gm. can be 

 obtained by adding water to the filtrate. 



The carotin crystallises from the petrol ether solution concentrated to 

 150 c.c. on adding 600 c.c. of 95 per cent, alcohol. Its yield is 0-3 gm. 



Carotin. 



Carotin is more easily prepared from carrots. The dried powdered carrot 

 is extracted in a percolator with petrol ether. The extract is concentrated in 

 vacuo at 40. Impure carotin crystallises out and is purified by solution in 

 carbon disulphide and fractional precipitation with alcohol ; the first precipitates 

 are the impurities. 



125 gm. of pure carotin are obtained from 5000 kilos, of fresh carrots or 

 472 kilos, of dried material, 



