Pure white candy should consist entirely of cane sugar with its water of crystallisation, but most of the article commonly met with contains a large proportion of glucose, and in many cases it is wholly composed of this compound (see p. 109). Starch and terra alba (i. e. gypsum or kaolin), are the other adulterants sometimes employed to fraudulently increase the bulk and weight of candy.

The substances used for colouring purposes are more liable to be positively deleterious. While such colouring agents as caramel, turmeric, litmus, saffron, beet-juice, indigo, and some of the coal-tar dyes may be considered comparatively harmless, there can be no question in regard to the very objectionable character of certain other pigments which are sometimes employed: these are mainly inorganic, and include plumbic chromate, salts of copper and arsenic, zinc-white, barium sulphate and Prussian blue. Another occasional form of adulteration to which some kinds of confectionery are exposed, is the admixture of artificial flavourings, such as “pear essence” (amylic and ethylic acetates), “banana essence” (a mixture of amylic acetate and ethylic butyrate), and oil of bitter almonds, or its imitation, nitro-benzole. A preparation known as “rock and rye drops,” which had acquired a great popularity among school children in several of our large cities, proved upon analysis to consist of a mixture of glucose, flour, and fusel oil.

The examination of candy and other forms of confectionery usually embraces the determinations of glucose, starch, flour, colouring and flavouring agents, terra alba, and mineral admixtures generally. The detection and estimation of glucose has already been described under Sugar.

Starch and flour are readily detected upon treating a minute portion of the suspected candy with a little water and submitting the mixture to a microscopic examination, when, in their presence, the insoluble residue will exhibit the characteristic forms of starch granules. The insoluble portion of the sample may also be tested with a solution of iodine. The proportion of starch can be determined by boiling the matter insoluble in water with dilute sulphuric acid, and estimating the amount of glucose found, by means of Fehling’s solution.

Coal-tar and vegetable compounds used for colouring purposes, can often, be recognised by means of their behaviour with reducing and oxidising agents, by their solubility in spirits and other menstrua, and by the application of dyeing-tests. Thus vegetable colours may sometimes be identified upon boiling mordanted cotton yarn in a bath prepared from a portion of the sample containing the colouring matter, and slightly acidulated with acetic acid. This process will likewise generally reveal the presence of aniline dyes, unmordanted woollen cloth being substituted for cotton, and a neutral bath being employed. The inorganic pigments used for colouring candy are usually to be sought for in the ash obtained upon incineration.

The presence of copper and lead is detected by the formation of black precipitates upon saturating with sulphuretted hydrogen the solution of the ash in hydrochloric acid; zinc, chromium, etc., are precipitated from the filtered solution upon addition of ammonium hydroxide and ammonium sulphide. It is frequently more convenient to apply special tests for the particular metal thought to be present, either directly to the pigment or to the ash. In this way, arsenic can often be recognised by treating a portion of the colouring matter in a test-tube, when it will sublime and collect upon the cool part of the tube in minute crystals of arsenious acid. Or, an acidulated solution of the detached pigments may be boiled with a piece of polished copper-foil, upon which the arsenic will be deposited as a greyish film: this can be sublimed, and otherwise further examined.

Copper is easily detected and estimated by placing the acid solution of the ash in a tared platinum dish, and reducing the copper by the electrolytic method. Chromium is recognised upon boiling the colouring matter with potassium carbonate solution: in its presence, potassium chromate is formed, which is submitted to the usual distinctive tests for chromium. The colour of Prussian blue is destroyed upon warming it with caustic alkalies: indigo, which remains unaffected by this treatment, forms a blue solution if heated with concentrated sulphuric acid. The presence of terra alba, barium sulphate, etc., is best detected by the examination of the ash. Chalk, or marble-dust, is recognised by its effervescence when treated with an acid, as well as by the presence of a notable proportion of lime in the ash.

Many of the flavouring mixtures added to candy may be separated by treating the sample with chloroform or petroleum naphtha and evaporating the solution to dryness over a water-bath, when their identity is frequently revealed by their odour and other physical properties. Of 198 samples of the cheaper varieties of confectionery examined by Health officials in the United States, 115 were adulterated. Plumbic chromate is a very common addition; 41 out of 48 samples of yellow- and orange-coloured candy contained this poisonous pigment.