Per cent. Substances soluble in water 61·33 Substances insoluble in water 36·45 Cellulose 9·78 Starch 8·34 Dextrine 49·51 Nitrogenous substances 11·87 Other non-nitrogenous substances 9·83 Fat 3·91 Ash 4·54 Moisture 2·22 “_Malt Coffee-substitute._” Per cent. { Albuminoid substances 4·22 Soluble { Dextrine 50·19 in { Alcoholic extract 7·57 hot water { Inorganic matter, } { containing } 2·27 { phosphoric acid, 0·54 } Insoluble in hot water 35·00 Moisture 0·35 The raw coffee bean is sometimes subjected to a process termed “sweating,” which consists in treating it with moist steam, the object being to artificially reproduce the conditions present in the holds of vessels, by means of which the bean is increased in size, and also somewhat improved in colour and flavour. Another form of manipulation, analogous to the facing of tea, is to moisten the raw bean with water containing a little gum, and agitate it with various pigments, such as indigo, Prussian blue, Persian berries, turmeric, alkanet, Venetian red, soap-stone, chrome-yellow, and iron ochre. Mexican coffees are sometimes made to resemble the more expensive Java in appearance. The chemist of the New York City Board of Health has found in the quantity of such treated coffee commonly taken to make a cup of the beverage 0·0014 gramme of cupric arsenite. Indigo may be detected in the artificially coloured product by treating a considerable portion of the sample with dilute nitric acid, filtering and saturating the filtrate with sulphuretted hydrogen. If indigo be present, it can now be extracted upon agitating the solution with chloroform. Alkanet root and Prussian blue are separated by warming the coffee with solution of potassium carbonate, from which these pigments are precipitated upon addition of hydrochloric acid. (_c_) _Microscopic Examination._--Great aid to the chemical investigation is afforded by the microscopic examination of ground coffee. It is necessary to first become familiar with the appearance of the genuine article--low magnifying powers being employed--and then make comparative examinations of the adulterant suspected to be present.