170 MISCELLANEOUS COMMUNICATIONS. 



On the Red Colouring of Fruit3 The red colouring matter of 



several kinds of fruits has in general been regarded as a blue colour, redden- 

 ed by an acid. This may be the case as to the colour of several fruits; but 

 all are not in the same predicament ; and consequently the colouring matter 

 of those which form the exception ought to be determined separately. Ber- 

 zelius examined the colour of the Cherry (Prunus census) and of the black 

 Currant ( Ribes nigrum), and found both to contain the same colouring mat- 

 ter, and the latter to be not blue. This presumption, perhaps, proceeds 

 from the fact, that the juice of these fruits gives, with acetate of lead, a blue 

 precipitate. These precipitates, however, are malate and citrate of lead, 

 with which the colouring matter is combined, and the latter may be with- 

 drawn from it, still slightly mixed with free acid, by a soluble quantity of 

 sulphuretted hydrogen ; and, after the separation of the acids, it is as to be 

 now described. 



To obtain it pure, it is requisite to separate the acids completely; and the 

 best agent for this purpose is chalk in fine powder, which causes a deposit of 

 malate and citrate of lime. Small quantities of lime are then added, in or- 

 der to precipitate the neutral malate of lime contained in the liquor, which is 

 next filtered and mixed with a little acetate of lead, when the green blue 

 then formed is separated, because it contains, peihaps, also malate of lead, 

 and whatever is in solution in the liquor is precipitated by acetate of lead. 



The green precipitate is collected on a filter, and washed in such a manner 

 that it may be always covered with water to prevent the access of air. It 

 is then decomposed by sulphuretted hydrogen ; the filtered liquor is evapo- 

 rated in vacuo over sulphuric acid ; the colouring matter left is dissolved hi 

 anhydrous alcohol, while the latter leaves undissolved the colouring matter 

 altered by the air, and pectine or pectic acid. By distilling the alcohol and 

 desiccating the residium in vacuo, the colouring matter is obtained in the 

 form of a beautiful red transparent brilliant mass. 



Much loss is sustained in determining at first, in the juice of these fruits, 

 bv the aid of acetate of lead, the presence of a blue precipitate of malate and 

 citrate of lead, then precipitating the colouring matter and the filtered liquor 

 bv the subacetate of lead, and decomposing the washed precipitate by sul- 

 phuretted hydrogen. In this state the colouring matter is soluble in all 

 proportions in water and in alcohol, but insoluble in ether. After evapora- 

 tion of its solution in the sand-bath it remains aqueous; but there is formed 

 a deposit less soluble in water, and very little soluble in alcohol, viz., ano- 

 ther red colouring matter less alterable. If to a solution of the colouring 

 matter in water there be added a little milk of lime, a gray green combina- 

 tion is precipitated. The colouring matter not yet precipitated is red, but of 

 another shade, because it contains a combination of lime with excess of colour- 

 ing matter. If the natural colour of the latter were blue, its solution would 

 be blue, and not red, because then every free foreign acid is saturated. The 

 colouring matter, 01; the contrary, forms, as has been seen, a combination 

 with the malate and the citrate of lead, and the latter is of a beautiful blue 

 colour ; but this colour presents nothing of the particular shade of the colour- 

 ing matter. The solution of the latter may be preserved without being ox- 

 idated ; nor is it oxidated so loug as it remains in contact with the free acid 

 in the juice of fruits. The brown red deposit is feebly soluble in water, to 



