The "apple.tannin" reaction is sometimes employed to distinguish between cider and factitious liquids containing no apple juice. About 10 c.c. of the liquid are extracted with an equal volume of ethyl acetate, the solvent is drawn off, and poured on to lime water in a test-tube. A band of yellow colour develops at the junction of the two liquids if the sample contains apple. juice. The colour is somewhat fugitive. If necessary, 100 c.c. of the sample may be evaporated down to about 10 c.c. before applying the test.

1 Official Publication, Cd. 1868, 1903.

For the estimation of tannin, Pi's method may be used. The reagents required are: -

(1) Solution Of Zinc Acetate

Dissolve 4 5 grains of crystallised zinc acetate in water, add ammonia solution until the precipitate produced is re-dissolved, and make up the volume to 200 c.c. with water.

(2) Solution Of Permanganate

0.558 Gram of KMn04 per litre.

(3) Solution Of Indigo

15 Grams of sublimed indigotin are dissolved in 15 c.c. of pure sulphuric acid, and after standing some days, the volume is made up to a litre. Each c.c. - 0001 gram of tannin.

To standardise the permanganate, 10 c.c. of the indigo solution and 10 c.c. of strong sulphuric acid are placed in a large flask, together with sufficient water to make the volume up to 1 litre. The permanganate solution is run in from a burette until the colour of the indigo is changed to yellow, and the volume required for this is noted, say N c.c. Then N c.c. = 001 gram of tannin.

To make the estimation, 10 c.c. of the cider are mixed with 5 c.c. of the zinc acetate solution, and evaporated in a porcelain basin on the steam-bath. Boiling water is then added, and the precipitate of zinc tannate filtered off, washed with hot water, and dissolved in dilute sulphuric acid (1 per cent. by vol.). This solution is then titrated with the permanganate. Suppose v c.c. are required. Then since N c.c. = 001 gram of tannin, v c.c. will = 001 x v/N gram of tannin, from the 10 c.c. of cider; so that in 100 c.c. of the cider the amount of tannin will be v/10N gram.

Boric acid is generally present in cider to a small extent quantities of the order of 0 005 to 0 020 per cent. having been found. To estimate it, 100 c.c. of the cider are mixed with a little calcium chloride (about 5 c.c. of a 10 per cent. solution), evaporated to dryness, the residue charred, boiled with about 150 c.c. of water, and filtered. The carbonaceous matter is incinerated thoroughly, but at not too high a temperature; then boiled with a further quantity (150 c.c.) of water, allowed to stand in the cold overnight, filtered cold, and the filtrate mixed with the first extract. (As a precaution, it is well to make a third extraction, testing this separately to show whether all the boric acid has been obtained.) The mixed liquids are then evaporated down to about 25 c.c, cooled, and exactly neutralised with iV/10.acid, methyl-orange being used as indicator. After adding an equal volume of glycerol (or preferably a few grams of mannitol), the solution is further titrated with

N/20.solution of sodium hydroxide, employing phenolphthalein as indicator this time. A little more glycerol or mannitol should be added to make sure that the end.point has been reached, as indicated by the pink colour remaining permanent after the addition. Each c.c. of the N/20.soda used represents 00031 gram of H3BO3.

The treatment with calcium chloride is designed to eliminate the phosphates in the ash, which would affect the titration. Calcium borate is moderately soluble in water, and is dissolved out on operating as described. According to Barker and Russell,1 the amount of phosphate present in cider ranges from 0.013 to 0.023 per cent., calculated as P2O5. The ash consists mainly of potassium carbonate and phosphate.

Analyses of various ciders are appended.

Analyses of cider.

Lloyd (loc. cit.) considers that cider should be regarded as "extra dry " if it contains not more than 2 per cent. of sugar, " dry " if the sugar is under 4 per cent. and "sweet" if above 4 per cent. The suggested "extra dry" limit strikes one as rather high.

Barker and Russell2 give a number of analyses of pure.juice cider, each made from a single variety of apple, and also a number representing blends of pure.juice ciders, denoting more the type of cider which finds its way to the market. These latter analyses are reproduced in the following table: -

1 Analyst, 1909, 34, 125. 2 Ibid., 130.

Dilution of cider with water will generally be indicated by deficiency in the proportions of alcohol and extract. Allen (loc.

cit.) considers that the original solids of unwatered cider rarely fall below 12 per cent. when calculated from the analytical results as follows: -

Alcohol, per cent. by weight X 207 Sugar fermented = + Acetic acid X1.5

Adding this to the percentage of solids still remaining in the sample, the sum equals the original solids of the juice before fermentation.

Perry is produced by the fermentation of the juice of fresh pears. It resembles cider very closely, but is generally somewhat less acid. In France, a good deal of the perry produced is distilled for the fabrication of eau-de-vie. The following analyses of English perry are given by Allen: -