Sel d'or occurs crystallized in fine needles, which are very soluble in water. The commercial article is often impure, containing little else than hyposulphite of soda, with a trace of gold. It may be analyzed by adding a few drops of strong nitric acid (free from chlorine) diluting with water, and afterwards collecting and igniting the yellow powder, which is metallic gold. Grape Sugar. Symbol, C{24}H{28}O{28}. Atomic weight, 366. This modification of sugar, often termed _granular sugar_, or _glucose_, exists abundantly in the juice of grapes, and in many other varieties of fruit. It forms the saccharine concretion found in honey, raisins, dried figs, etc. It may be produced artificially by the action of fermenting principles, and of dilute mineral acids, upon starch. _Properties._--Grape sugar crystallizes slowly and with difficulty from a concentrated aqueous solution, in small hemispherical nodules, which are hard, and feel gritty between the teeth. It is much less sweet to the taste than cane sugar, and not so soluble in Water (1 part dissolves in 1-1/2 of cold water). Grape sugar tends to absorb oxygen, and hence it possesses the property of decomposing the salts of the noble metals, and reducing them by degrees to the metallic state, even without the aid of lights The action however in the case of _nitrate of silver_ is slow, unless the temperature be somewhat elevated. _Cane_ sugar does not possess these properties to an equal extent, and hence it is readily distinguished from the other variety. Honey. This substance contains two distinct kinds of sugar, grape sugar, and an uncrystallizable substance analogous to, or identical with, the treacle found associated with common sugar in the cane juice. The agreeable taste of honey probably depends upon the latter, but its reducing power on metallic oxides is due to the former. Pure grape sugar can readily be obtained from inspissated honey, by treating it with alcohol, which dissolves out the syrup, but leaves the crystalline portion. Hydrochloric; Acid. Symbol, HCl. Atomic weight, 37. Hydrochloric acid is a volatile gas, Which may be liberated from the salts termed chlorides by the action of sulphuric acid. The acid, by its superior affinities, removes the base; thus,-- NaCl + HO SO{3} = NaO SO{3} + HCl. _Properties._--Abundantly soluble in water, forming the liquid hydrochloric or muriatic acid of commerce. The most concentrated solution of hydrochloric acid has a sp. gr. 1·2, and contains about 40 per cent, of gas; that commonly sold is somewhat weaker, sp; gr. 1·14 = 28 per cent. real acid. Pure hydrochloric acid is colorless, and fumes in the air. The yellow color of the commercial acid depends upon the presence of traces of perchloride of iron or organic matter; commercial muriatic acid also often contains a portion of free chlorine and of sulphuric acid. Hydriodic Acid. Symbol, HI. Atomic weight, 127.