MISCELLANEOUS COMMUNICATIONS. 169 



crystallization, and they might be drawn by the fingers into a yellow unctu- 

 ous fat. This is mixed with a small quantity of fat oil which Berzelius 

 could distinguish but not isolate with certainty, and with another substance 

 equally as fat. It could be detached in greater degree from the first sub- 

 stance, by digestion with a weak solution of caustic potass, which saponifies 

 the oil and dissolves only a small quantity of the yellow fat. The yellowish 

 fat acids are precipitated from the alkaline solution by hydrochloric acid, and 

 by redissolving them in very much diluted caustic ammonia (five or six 

 drops of the aqua ammonia to one ounce of water) and again precipitating 

 them, they are obtained colourless. To deprive it of the last substance, or 

 the solid fatty matter, it is necessary to treat it with cold alcohol, in which 

 it is not soluble. He was, however, never able to obtain it completely free 

 from these two fat substances. 



The yellow fat is soluble in alcohol, though in small quantity. In this 

 solution it is not sensibly whitened at the same time as it begins to whiten 

 with water. The alcoholic solution furnishes a precipitate on the addition 

 of water ; it then assumes a pale, milky-yellow aspect, with difficulty becomes 

 clear, and also preserves this state after the evaporation of the alcohol. From 

 the alcoholic solution it is deposited by spontaneous evaporation, under the 

 form of a granular crystaline mass. It is copiously dissolved by ether, and 

 it remains, after the evaporation of the solvent, transparent and of a yellow 

 colour. In contact with concentrated sulphuric acid, it becomes brown, is 

 sparingly dissolved, but with alteration, and furnishes then a brown-yellow 

 liquor, which is precipitated by water in a white gray. In caustic potass 

 it is very sparingly dissolved, and exposed in this solution for some time to 

 the influence of air and light, it is bleached. From the solution in potass it 

 is precipitated by acids in pale yellow flakes, which, if properly washed, do 

 not redden turnsol infusion. In carbonate of potass it is little or not at all 

 soluble, and insoluble in caustic ammonia, to which, nevertheless, it imparts 

 a yellow colour. 



This yellow colouring matter is therefore a peculiar fatty substance, inter- 

 mediate between the fat oils and the resins, which may be bleached, retain- 

 ing, however, its property of being with difficulty soluble in alcohol, and of 

 being fat and unctuous. To this Berzelius proposes to apply the epithet of 

 Xanthophylle from lavSos, yellow, and <pv\Xov, leaf or foliage. He thinks 

 there is every reason to presume that in the disappearance of the green 

 colour and its conversion into yellow, the latter arises from the green by 

 virtue of a change in the organization of the leaf effected by cold, and which 

 modifies the organic process. He has in vain, however, attempted to repro- 

 duce the green colour with the yellow ; and he has been equally unsuccessful 

 in converting the green into yellow. 



The brown colour of the foliage presents no common character with the 

 yellow. It is produced by an extractive principle, at first colourless, which, 

 after the disorganization of the epidermis of the foliage, becomes brown by 

 the action of oxygen, and then communicates to the fibre of the skeleton of 

 the foliage a brown tint, which cannot be removed even by digesting it with 

 a weak solution of caustic potass, and cannot be destroyed by long continued 



treatment with sulphuretted hydrogen Berzelius, Annalcn tier Pharma- 



cie, vol. xxi, st. 3, p. 257. 



VOL. VIII., NO. XXIII. 23 



