A standard solution of pure cupric sulphate is first prepared by dissolving 34·64 grammes of the crystals (previously ground and dried by pressing between bibulous paper) in about 200 c.c. of distilled water; 173 grammes of pure Rochelle salt are separately dissolved in 480 c.c. of a solution of sodium hydroxide of sp. gr. 1·14. The solutions are then mixed and diluted with distilled water to one litre. Each c.c. of the above solution represents 0·05 gramme of grape sugar. The test is applied by taking 10 c.c. of the copper solution, adding about four times its volume of water, and bringing it to the boiling point. The coffee infusion is then gradually added from a burette, until the copper salt is completely reduced to the red sub-oxide, which point is recognised by the disappearance of its blue colour, and can be more accurately determined by acidulating the filtered fluid with acetic acid and testing it (while still hot) for any remaining trace of copper with potassium ferrocyanide. In preparing the coffee solution for the foregoing test, it is advisable to exhaust a weighed quantity of the sample with hot water. The infusion is treated with basic plumbic acetate so long as a precipitate forms; it is then filtered, the precipitate being well washed, and the lead contained is removed by conducting sulphuretted hydrogen gas through the fluid which is subsequently again filtered and boiled until the dissolved gas is expelled. The sugar determination is now made. Wanklyn employs the following equation to estimate the amount of chicory in an adulterated sample:-- E = ((S - 1)100) / 14, where E is the percentage of chicory, and S the percentage of sugar. According to the analysis of König, the proportions of sugar and other constituents in some of the adulterants of coffee, are as follows:-- ----------------------------+---------+---------+---------+--------- |Chicory. | Figs. | Acorns. | Rye. ----------------------------+---------+---------+---------+--------- |per cent.|per cent.|per cent.|per cent. Water | 12·16 | 18·98 | 12·85 | 15·22 Nitrogenous substances | 6·09 | 4·25 | 6·13 | 11·84 Fat | 2·05 | 2·83 | 4·61 | 3·46 Sugar | 15·87 | 34·19 | 8·05 | 3·92 Other non-nitrogenous | 46·71 | 29·15 | 62· | 55·37 substances. | | | | Cellulose | 11·0 | 7·16 | 4·98 | 5·35 Ash | 6·12 | 3·44 | 2·12 | 4·81 Substances soluble in water | 63·05 | 73·8 | .. | 45·11 ----------------------------+---------+---------+---------+---------