The Detection of the Adulterations of Curry Powder.

The adulterations of curry powder, with the exception of potato farina or starch, met with in one sample, being the same as those of Cayenne, the methods for their discovery are also the same; the reader is therefore referred to the article on 'Cayenne.'

The presence of potato starch is detected by means of the microscope; the characters of its granules are described under the head of 'Arrowroot.'

CHAPTER XXXV.

TURMERIC AND ITS ADULTERATIONS.

DEFINITION OF ADULTERATION.

Any added vegetable or mineral substance.

TURMERIC powder consists of the ground tubers of a plant belonging to the same genus as ginger, viz. Curcuma longa, and which is extensively cultivated in India and China.

Composition of Turmeric.

The composition of turmeric is shown in the following analysis :

To extract curcumin, the pulverised root is boiled with water, the residue treated with boiling alcohol; the alcoholic solution is filtered, evaporated, the residue digested with ether, and the ethereal solution in its turn evaporated, when the curcumin is obtained, together with a little essent oil.

It is heavier than water, in which it is insoluble, but dissolves readily in alcohol, ether, and in fixed and volatile oils. It melts at 40° C.

The alcoholic solution of turmeric is characterised by its beautiful green fluorescence; the spectrum of the solution not exhibiting any peculiar dark or bright bands. The fluorescence is best seen by placing the solution of turmeric in alcohol or benzol in a small beaker

and concentrating the rays of the sun in the solution by means of a burning-glass, when the illuminated cone thus produced will appear bright green.

Structure of Turmeric.

The structure of the tuber of turmeric is well exhibited in the annexed figures.

a a, epidermis; bb, transparent cells; cc, yellow masses; d d. oil globules;
e e, resinous masses: f, dotted duct; g, elongated cells of woody fibre, lying
by the side of the duct.

Turmeric powder consists of large cells; some of these are loosely imbedded in a reticular tissue, but others, and these the majority, are quite free; they may be recognised with facility, under the microscope, by their size and bright yellow colour (fig. 195).

When crushed, each cell is found to contain colouring matter as well as a number of starch granules, resembling closely those of Curcuma arrowroot, already described and figured (fig. 196).

On the application of iodine the cells become of a deep blue, and with potash, of a reddish colour.

THE ADULTERATIONS OF TURMERIC.

Of fourteen samples of turmeric powder subjected to examination, two were adulterated with yellow ochre, to the extent of nearly 20

This engraving represents the appearance and characters of genuine ground
TURMERIC. Drawn with the Camera Lucida, and magnified 220 diameters.

per cent., while nearly all the other specimens contained considerable quantities of alkali, carbonate of soda or potash, added no doubt to heighten the colour of the powder.

Inasmuch as turmeric enters so largely into the composition of curry powder, mustard, and some other condiments, it became necessary to ascertain whether it was liable or not to sophistication.

The Detection of the Adulterations of Turmeric.

Yellow ochre consists of oxide of iron diluted with chalk; the ash of turmeric powder must therefore be tested in the manner already elsewhere directed for the detection of those two substances.

The

presence of the ochre is in general sufficiently indicated by the colour and weight of the ash.

Should the ash, say, of 10 grammes of the turmeric contain alkali, as carbonate of soda or potash, we must proceed as follows: the alkali must be dissolved out of the ash by means of distilled water. The solution is coloured blue by means of a drop of tincture of litmus, and the amount of alkalinity is ascertained by the addition from a graduated burette of a standard solution of sulphuric acid, the change in the colour of the litmus indicating the end of the reaction.

For the determination and estimation of potash and soda the processes will be found given in the article on 'Tea.'

It is always well to test, before commencing the analysis, the reaction of the watery solution of the ash, as, unless this is decidedly alkaline, it does not contain alkali, and again it is proper also to test the ash, to ascertain whether salt has been used, and which is sometimes employed to heighten the colour of vegetable powders. Very generally the presence of alkali in the ash of turmeric powder is sufficiently indicated by the greenish colour, more or less intense, exhibited by it when first removed from the fire.