are large oval or pyriform cells, often containing shrivelled cell contents. Common measurements of these cells are 008 inch small diameter, 0176 inch long diameter for the oval cells, and for the pyriform 0136 inch broad end, 0184 long diameter.

A general analysis of strawberries has been published by J. M. H. Munro. (Chem. News, 1., 227.)

Sulphuric anhydride,

Sand and insoluble matter,
Undetermined,

The Raspberry has its seeds reticulated, and in most jams the form of the fruit is preserved quite sufficiently for recognition.

The Gooseberry has an epidermis in which can be seen a mosaic pavement of cells, and the fruit also possesses clavate hairs.

The Blackberry-the seeds are reticulated, and the cuticle covered with stellate hairs.

Currants. Both the black and the red currant are similar in structure: the epidermis is covered with an ex- Fig. 24.-a, Pulp cells of cessively thin membrane, showing sinu- strawberry, x 115; b,strawberry seed, x 20. ous wavy divisions, and set with simple

hairs. Beneath the outer membrane are the colour layers, consisting of little square masses with rounded angles about 00029 to 00039 inch diameter (a, fig. 25). The pulp is made up of thin-walled cells, and, lastly, here and there may be found peculiar compound bodies, b, attached to the inner layer of the epidermis. These are about 0058 inch in length and .0015 inch in breadth, and are formed of a number of oblong cells. So far as known, these bodies are found only in the currant.

Fig. 25.-a, A shred of epidermis, showing the sinuous markings in one portion, and the under layer of cells in another; b, the compound bodies, x 115.

SACCHARIN.

This is the popular name given to a crystalline substance discovered by Fahlberg and Remsen (Deut. Chem. Ges. Ber., xii., 469-573) in 1879. It was first obtained by the oxidation of orthotoluene sulphonamide by permanganate; its formula is C-H5O3SN, and it has been named anhydro-ortho.CO. sulphamine-benzoic acid C6H4 <SO2 >NH --or, shorter, Benzoic sulphamide—it is in the form of white crystals, soluble in hot water, alcohol, and ether. It melts at 220°, and can be sublimed without undergoing decomposition; it forms crystalline compounds, with the alkalies and alkaline earths; on evaporating an aqueous solution strongly acidified with HCl, almost to dryness, it is transformed into ortho-sulpho-benzoic acid. It is so intensely sweet that 1 part in 10,000 of water is very perceptible; the sweetness is like that of sugar, but with a peculiar flavour. The substance is used in commerce, and the analyst will look for it in all sweet manufactured liquids, such as lemonades, temperance drinks, and liqueurs; it is said also to be added to sugar itself, to increase its sweetening power. It is not poisonous, but, on the other hand, it has no nutritive powers; it is said to pass through the kidneys unchanged. A general method of detecting saccharin is to shake liquids, after feebly acidifying, with ether; to separate the ether and evaporate to dryness. The ethereal extract obtained in this way, if saccharin be present, will taste extremely sweet, and if the residue is gently fused in a platinuin dish with six times its weight of pure sodie carbonate and potassic nitrate, the sulphur will be oxidised into sulphate, and the fused mass will, when dissolved and the solution acidified with HC, give a precipitate with baric chloride.

Saccharin fused gently with potash is converted into salicylic acid, and, therefore, with ferric chloride strikes a violet colour.

Solids, such as sugar, are also treated with ether, and the ethereal extract examined as before; but if the solid has an alkaline reaction, it is best first to extract with hot water, acidify the aqueous solution, and shake out with ether.

Fatty substances or liquids must first be freed from fat, by treatment with light petroleum. A quantitative estimation is most accurately made by oxidation of the sulphur by fusion and precipitating the sulphate with barium chloride-1 part of barium sulphate equals 785 of saccharin.

STARCH, C6H1005.*

§ 80. It is convenient to consider the starches together, more especially as, however varied in form, the chemical composition of all starch is very similar, if not identical.

Every starch corpuscle is composed of at least two probably isomeric bodies, the one "granulose," soluble in saliva, and coloured blue by iodine; the other coloured by iodine pale

T. Pfeiffer and B. Tollens (Lieb. Annalen, 285-309) have prepared compounds of the alkalies with the carbo-hydrates, and from the data thus obtained consider the formula of starch to be either C24H40020 or C24H40020 + H2O, and according to this formula, the amount of dextrose yielded by starch should be 108 11 per cent.

yellow, and only becoming blue after the addition of sulphuric acid; it is fully soluble in ammoniacal oxide of copper, and appears to agree very closely with the characters of cellulose.

These two substances may be most readily separated by diluted chromic acid, which dissolves granulose very easily, whilst cellulose remains unaltered. All starch is very hygroscopic: wheat starch, dried in a vacuum, still contains 11 per cent. of water, and air-dried from 16 to 28 per cent. of water. Starch is insoluble in cold water or spirit. Some chemists, indeed, assert that if finely powdered in agate mortars, or with quartz sand, a small portion dissolves; others contend that this is no true solution, but the starchy matter in a state of most minute division. If warmed with water, the starch granules swell, and when heated up to 100° most starches form a semi-solution in water. True compounds of starch with bases are scarcely established. Lime and baryta appear to form weak unions, and the intense colour produced by iodine, as well as bromine, seems to point to the formation of haloid combinations. Fritsche, indeed, states that he has isolated the iodide and the bromide of starch, the former containing ten equivalents of starch and one of iodine.

Starch heated in closed tubes up to 100° changes gradually into soluble starch. If the temperature is raised up to 160° or 200°, it forms a transparent mass, consisting wholly of dextrin. At 220° to 280° still further change is produced, and the result is pyrodextrin, a substance easily soluble in water (but insoluble in absolute alcohol and ether), and with the composition of C48H36O36HO. At still higher temperatures there is carbonisation, and the formation of products similar to those caused by the decomposition of sugar.

Starch is easily changed into sugar by the action of dilute mineral acids, as well as by oxalic acid, aqueous chloride of zinc, and by certain ferments-diastase, saliva, yeast, &c.

The estimation of starch in organic bodies is always based upon converting it into glucose and estimating the glucose. This conversion is done in various ways. 1 to 13 grms. may be heated in closed tubes or flasks, in 40-50 cc. of 2 per cent. sulphuric acid for eight hours in a glycerin bath to 108° or 110°; or the substance, in some instances, may be heated in ordinary flasks in the water-bath, with a 2 per cent. solution of hydrochloric acid, for many hours until it ceases to give a starch reaction with iodine.

An excellent general method has been proposed by Dragendorff:-2 to 3 grms. of the powdered and dried substance are heated, with 25 to 30 cc. of a 5 per cent. solution of potash in absolute alcohol, for from eighteen to twenty-four hours in the

water-bath, filtered hot, through a weighed filter, which is ash free; the residue on the filter is washed first with hot absolute and then with cold ordinary alcohol, and lastly with water-the residue is now dried at 110° and weighed, the loss of weight corresponds to the albuminoid matters, the fat, the sugar, and the soluble salts, which have been removed by the alcoholic potash, the alcohol, and the water. The filter and its contents are now divided finely by scissors, and boiled with 5 per cent. hydrochloric acid until a blue colour is no longer struck with iodine, the liquid is then filtered through a weighed filter, and the residue washed, dried, and weighed the difference between the weights of Nos. 1 and 2 gives very nearly the starch. This weight may, of course, be controlled by estimating the glucose by Fehling.

A general method for the estimation of starch in flours has been worked out by C. O. Sullivan (Journ. Chem. Soc., Jan. 1, 1884, No. ccliv., 2-10); its principle is the freeing of the finely divided substance from fat, albuminoids, and amylans by suitable solvents, and then transforming the starch by the action of diastase into maltose and dextrin, the proportions of which are estimated by the Fehling solution and by the polariscope.

1. Preparation of the Diastase.

2 to 3 kilos. of finely-ground pale barley malt are steeped in water just sufficient to cover the whole. After standing several hours it is filtered by means of a filter press; and if not clear by passing it also through an ordinary filter. The diastase is now precipitated by alcohol sp. gr. 83, the alcohol being added so long as the precipitate is flocculent, but discontinued when a milky or opalescent appearance commences. The diastase is washed with alcohol (86-88), dehydrated with absolute alcohol, and dried in vacuo over sulphuric acid. Diastase thus prepared is a white, dry, friable, soluble powder retaining its activity for a long time.

Freeing the flour from fatty matters.—5 grms. of the flour are first saturated with alcohol sp. gr. 82, and from 20 to 28 cc. of ether added. The flask containing the mixture is set aside for a few hours, and the whole is then filtered; the residue being washed with ether.

2. Removal of Sugars, Albuminoids other than Casein,
and Matters soluble in weak Alcohol.

To the flour now fat free, 80 or 90 cc. of alcohol sp. gr. 90 are

added, and the mixture kept at 35° to 38°, with occasional shaking for a few hours. The alcoholic solution is then passed through the same filter which has been used for the "ether" operation, and the residue washed by decantation with the same strength alcohol, and at the same temperature.

3. Solution of the Amylans:

The flour which has been treated with alcohol and ether, is now submitted to the action of water; the flour is digested with half a litre of water, and decanted through a filter at the end of twenty-four hours; it is then repeatedly washed with water at 35° to 38°.

This part of the operation is tedious, for the filtration is sometimes very slow.

4. Conversion of the Starch.

The residue is finally transferred to a beaker, and boiled for a few minutes in 40 or 45 cc. of water with constant stirring-it is then cooled to 62° or 63°, and 021 to 038 grm. diastase dissolved in a few cc. of water added. In a very short time the solution ceases to give a starch reaction with iodine, but it is best to maintain the digestion for an hour, because filtration is then easier. At the end of that time the contents of the beaker are boiled for eight or ten minutes, thrown on to a filter, and the filtrate received into a 100 cc. measuring flask. The residue is carefully washed with small quantities of boiling water at a time. When the flask is nearly full, its contents are cooled down to 15°5, and made up to 100 cc. with water at that temperature. Should the filtrate exceed 100 cc., it is to be concentrated to the proper quantity. The specific gravity of the solution is now taken; its optical activity is determined, and its reducing power on copper solution estimated by boiling with Fehling.

=

+ 222° (αp

=

=

The optical activity of maltose Mr. Sullivan gives for the concentrations to be dealt with as [a], = 154° (a: + 139°), and that of dextrin [a], +200-4); with these values 1 grm. maltose in 100 cc. solution gives a deviation with a Soleil-Ventzke-Scheibler saccharimeter in a 200 mm. tube = 8·02 divisions, and 1 grm. of dextrin in 100 cc. in the same length of tube 11.56 divisions; if the observations are made with any other sodium flame polarimeter, the factors proper to these instruments must be substituted. An example from Mr. Sullivan's paper will make the above clear.