colouring is only on the external surface, it is better to detach it by scraping or rasping, than to powder the whole substance up, for if the colour is carefully detached as pure as possible, tests may sometimes be directly applied without any further trouble. The colour by treatment with alcohol, with water, and with bleaching powder, is quickly referred either to the organic or to the inorganic division of chemical substances. With regard to organic colours generally, the reader may consult the sections treating of "Colour," where full directions are given for their identification. If, however, the colour is apparently inorganie, then the following substances may be particularly tested for :— Among RED colours-iron;

YELLOWS―chromate of barium, and lead compounds,
arsenic and antimony;
GREEN-arsenic, copper ;

BLUE-Prussian blue;

WHITE-sulphate of barium, salts of zinc.

A weighed portion of the scraped-off colouring-matter is burned to an ash, which is dissolved in hydrochloric acid, and tested with hydric sulphide, after adding just sufficient soda to so neutralise the acid as to leave only a slight excess. Under these circumstances, lead, copper, or zinc, if present, will be precipitated; while, if it is strongly acid, zinc would remain almost entirely in solution. Ammonium hydrosulphide is next added to the solution, which has been boiled and filtered from any precipitate; this reagent will throw down iron, manganese, &c. To test for chromium, it is best to boil the colouring-matter with a solution of carbonate of potassium, when potassic chromate will be formed, which gives, in neutral solutions, a purplish precipitate with nitrate of silver. Barium is easily detected by fusing the ash with carbonate of soda, dissolving the ash in dilute hydrochloric acid, and adding a little hydric sulphate; a heavy characteristic precipitate of barium sulphate is thrown down. If barium is present, it may exist with evidences of chromium, in which case, in all probability, the colouring-matter was chromate of barium, or if the sweetmeat is not coloured by barium chromate, baryta sulphate may have been added simply to give weight. Arsenic and antimony are best discovered by boiling a little of the colouring-matter with copper-foil [Reinsch's test]; and although this test will not detect quite such a minute quantity as Marsh's test, it is sensitive enough. Copper is also best detected by electrolysis, the substance being placed in a platinum dish, acidified, and then a rod of zinc inserted; or, the neater plan of connecting the dish itself with a battery may, where appliances are at hand, be preferred.

HONEY.

§ 76. Commercial honey is the saccharine matter collected and stored by one particular species of bee (Apis mellifica); but the production of honey is by no means limited to the bee, for there is a honey-ant* in Mexico, which stores a nearly pure syrup of uncrystallised sugar. This is slightly acid in reaction, and reduces salts of silver like formic acid.t

From determinations of the amount of saccharine matter in different flowers, it has been calculated that to make 1 kilogramme of honey, the bees must visit from 200,000 to 500,000 flowers.

A wasp of tropical America is said to yield a honey in which are found crystals of cane sugar, but the evidence as to this latter point is not decisive. A curious sample of honey has been analysed by A. Villiers.§ It was derived from Ethiopia, and is the produce of an insect resembling a large mosquito, which, like our wasp, makes its nest in cavities in the ground. It secretes no wax. The natives call the honey "tazma," and ascribe to it medicinal virtues, especially using it as a cure for sore throat. Its composition is as follows:

Water,

Per cent.
25.5

Fermentable sugar (levulose with a sixth of glucose in excess), 320
Mannite,

Dextrin, .

Ash,

3.0

27.9

2.5

9.1

Loss and unestimated,

The honey contained a non-nitrogenous bitter principle.

The essential constituent of honey is a mixture of dextrose and levulose; it also contains mannite, wax, formic and other organic acids, pollen, not unfrequently alkaloidal and bitter principles from the plants, possibly derived from the pollen, small quantities of cane sugar, of mineral matter, and invariably minute quantities of alcohol.

The properties of dextrose and levulose have been already described. The other saccharine constituent of honey-mannite, CH1406-crystallises in four-sided prisms, is soluble in 80 parts of alcohol of specific gravity 0·898, and in 1.400 parts of absolute

* The Myrmecocystus Mexicanus. There are two kinds of workers-one the active form, the other sedentary-which produce the honey. The latter is the larger, and has a tumid abdomen; it never quits the nest. The honey is discharged into proper receptacles, and from it the Mexicans make a pleasant drink.

+ H. Marsten, Pogg. Ann., c. 550.

G. M. Wetherell, Chem. Gaz., 1853, 72. § Compt. Rend., lxxxviii. 292, 293.

alcohol; in boiling alcohol it is more soluble, but in ether it is quite insoluble, and may be precipitated from alcoholic solution by ether. It has no action on polarised light. Its melting point is from 160° to 165°; at 200° it boils, and may be distilled, a portion being decomposed; at higher temperatures it carbonises. It does not reduce cuprous oxide. All these properties readily distinguish it from the other sugars. Chemically speaking, mannite is a hexatomic alcohol. Mannite may be separated from honey by boiling a weighed quantity of the honey with alcohol, evaporating down the alcoholic extract to dryness, and boiling this extract with absolute alcohol, concentrating the alcohol solution, and precipitating with ether.

Dr. Brown has published some analyses of honey, in which the different sugars have been identified; the general results of six of his samples may be thus stated :

Water (expelled at 100°),

Water expelled at a much higher temperature and loss,
Levulose,

Dextrose,

Ash,

The chief results of twenty-five analyses made by Mr. Hehner* of honey believed to be genuine, are as follows:

Dr. E. Sieben has published analyses of sixty samples of honey which he believed to be perfectly genuine the general results are as follows:

The chief adulteration of honey is the addition of starch sugar in the form of syrup. Cane sugar may be also found, and mineral adulterations are possible. Starch sugar may be detected by dialysis (0. Haenle). 200 grms. of honey are dissolved in water, made up to a litre, and the solution placed in a dialyser, so arranged that the outer vessel has a continuous stream of water running through; at the end of fourteen hours, the solution in the dialyser is decolorised by charcoal, suitably concentrated and examined by polarised light; natural honey treated in this way has no effect, but starch syrup turns the ray to the right.

Mr. Hehner determines the moisture at 100°. The glucose is estimated by Fehling's solution-both before and after inversion, the inversion is produced by heating with 10 per cent. of hydrochloric acid to about 70°. The rotatory power of a 10 per cent. solution is determined both before and after fermentation. The fermentation is produced in a 10 per cent. solution by the addition of a little yeast, the vessel being kept in an incubator at 30° for from five to six days; this operation might be made more speedy by fermenting in a vacuum with plenty of yeast, as suggested by Boussingault. After fermentation, the solid matter is determined and subtracted from the percentage of glucose left unfermented. The proportion of unfermentable matter should be no larger than would be yielded by a pure glucose solution after fermentation, viz., about 5 per cent.

A pure honey has the following characters :-The moisture does not exceed 23 per cent. The percentage of glucose before and after inversion is about the same. The unfermentable

"Ueber die Zusammensetzung des Stärkezuckersyrups, des Honigs, u. über die Verfälschungen des letzeren." Zeitschrift der Ruben Zucker. Ind., 1884, 837. + It is doubtful whether cane sugar occurs in pure honey-although Sieben gives 8-22 per cent. of cane sugar as a possibility in pure honey, he yet returns a honey containing 7 per cent. of cane sugar as adulterated, two statements that cannot be reconciled.

The honey derived from flowers turns a ray of light to the left, that from conifers to the right; it is obvious that honey derived from both species of plants may either have no influence on light, or deviate right or left, according to circumstances.

TABLE IX.-SOME ADULTERATED SAMPLES OF HONEY ANALYSED BY E. SIEBEN.

1.

2. 3.

4. 5.

6.

7. 8.

9.

10.

11.

12.

37.20 31.80 6918
21.75 1960 41:30
34.6123.89 | 58.83
25:47 23:51 49:04
21.92 12-83 35:00
30:00 22:30 | 52:56

about 15% starch sugar syrup.

65 07