THE PIGMENTS OF LEAVES 531 



Properties of Carotin. 



Carotin crystallises in rhombohedra and in rhombic platelets of bright 

 copper-blue colour, red in transmitted light. It melts at about 174. 



Carotin is easily soluble in benzene, chloroform and carbon disulphide. 

 The solutions in the two former solvents are yellow, in carbon disulphide 

 red in colour. It is soluble with difficulty in boiling ethyl and methyl alcohols 

 and acetone, almost insoluble in the cold. 900 c.c. of boiling ether, or i -5 

 litres of boiling petrol ether, dissolve i gm. 



It dissolves in concentrated sulphuric acid giving an indigo-blue solution. 

 It is an unsaturated compound and undergoes auto- oxidation. The crystals on 

 exposure to the air lose their colour and about 35-40 per cent, of their weight. 

 With iodine it forms a deep violet addition compound of the formula C 40 H 5(5 l2- 



Its spectrum in alcoholic solution shows two bands in the blue region with 

 absorption of the violet end ; in carbon disulphide solution there is a band in 

 the green and a band in the blue. 



Properties of Xanthophyll. 



Xanthophyll forms long platelets of a yellow to red colour in transmitted 

 light with a steel blue lustre. It melts at 173-174. Xanthophyll is easily 

 soluble in chloroform, with difficulty in carbon disulphide, insoluble in 

 petrol ether, i gm. dissolves in 300 c.c. of boiling ether, in 700 c.c. of boil- 

 ing ethyl alcohol, in 5000 c.c. of cold alcohol. Its solutions have a yellow 

 colour. It behaves like carotin towards air, concentrated sulphuric acid and 

 halogens. 



Its spectrum in alcoholic solution is very similar to that of carotin ; in 

 carbon disulphide there is a third band in the blue region. 



Fucoxanthin. 



The brown algae are extracted as described on p. 524 in the same way as 

 chlorophyll from fresh material and the chlorophyll is precipitated. The nitrates 

 from 15-20 kilos, material occupying a volume of 40 litres are mixed in portions 

 of 4 litres with i litre of a mixture of 3 volumes of petrol ether and i volume 

 of ether and treated with 1500 c.c. of water. The aqueous acetone layer of a 

 yellow-green colour is removed, the ether-petrol ether solution is freed from 

 acetone by washing and concentrated to 500 c.c. This solution is mixed 

 with 500 c.c. of ether to dissolve the fucoxanthin which separates. The 

 xanthophyll and fucoxanthin present in the solution are separated by shaking 

 4 times with i litre and twice with 500 c.c. of 70 per cent, methyl alcohol 

 saturated with petrol ether. The xanthophyll in the methyl alcoholic solution is 

 removed by shaking it with an equal volume of a mixture of 5 volumes of 

 petrol ether and i volume of ether. The fucoxanthin which also dissolves 

 is recovered by evaporating it in vacua, diluting with ether, and shaking twice 

 with 70 per cent, methyl alcohol ; these solutions are also washed with the 

 ether-petrol ether mixture. The fucoxanthin in the methyl alcohol is trans- 

 ferred into ethereal solution by adding water, the ether is evaporated off and 

 the fucoxanthin is precipitated by adding i litre of petrol ether per 200 c.c. 

 About 2 gm. are obtained. 



Fucoxanthin is easily soluble in all organic solvents except petrol ether 

 and methyl alcohol. It crystallises from methyl alcohol in monoclinic brown- 

 red prisms with a blue lustre. It melts at 159-160. The ethereal solution 

 is orange-yellow in colour, the alcoholic is brownish, the carbon disulphide one 

 is reddish. 



It forms a crystalline addition product with iodine and has a slight basic 

 character, 



