The remaining aqueous solution contains the whole of the constituents of cacao or chocolate which are soluble in water. It is measured into a graduated cylinder and its volume ascertained. Then, after the entire amount has been evaporated to dryness, the residue is calculated on a percentage basis. The following procedure, however, is preferable. 10 ccm of the liquid are evaporated and the residue well dried in a vacuum before it is weighed. Multiplying the ascertained weight by 10, we obtain the amount of cacao or chocolate soluble in water and present in 5 and 10 grammes of either substance respectively. The amount of ~sugar~ in the aqueous extract can be determined in the following manner. 50 ccm of the extract are heated in a water bath and thus separated from ether; afterwards 2 ccm of lead acetate are added and the whole immediately transferred to a special kind of filter paper. The solution is now polarised in the usual way and the number of grammes of sugar thus ascertained converted into ccm by division (1·55 being the unit) and then the result subtracted from 100, which gives the volume of water present in 100 ccm of sugar solution, and so by further division until the percentage of sugar in chocolate is finally obtained. If the polarisation yields more sugar than the weight of the total residue, it is an indication that dextrine is present as an adulteration. The quantitative determination of dextrine, which is sometimes added to cocoa powder as well as to chocolate, for like gelatine and tragacanth it holds water together and so ensures a saving of fat, is best carried out in P. Welman’s polarising method.[172] As the amount of fat obtained from 5 grammes of a cacao preparation does not suffice for tests of purity, a larger quantity must be extracted in order to carry out the following investigations. This has reference to 1. The determination of the melting point; 2. The determination of the iodine value (Welman)[173]; 3. The determination of the saponification value; 4. The determination of the acid value; 5. The determination of the Reichert-Meissl value; 6. Polen’s value[174]; 7. Cohn’s investigation[175]; 8. Melting point of the fatty acids; 9. Refraction of the fatty acids; 10. Iodine value of the fatty acids; 11. Determination of the refractive index at 40° C. in Zeiss’ butter refractometer. The following process is usually adopted in the determination of the melting point of cacao fat: The melted fat is sucked up a glass capillary tube, the internal diameter of which does not exceed 2 mm (fluctuating between 1·8 mm and that measurement) to somewhat above the part of the tube which is graduated into tenths, and then so much of the capillary tube cut off as suffices to make the fat column there half the height of the bulb of the mercury thermometer used in the experiment.