2. ~Estimation of ash~[165]: 5 grammes of material are heated in a platinum vessel, pan or flat tray, the latter or other similar shallow receptacle being the most suitable, holding from 25 to 30 cubic centimetres. Care should be taken when heating that the extremity of the Bunsen flame only touches the bottom of the vessel. The resulting gases are then ignited, and the ~completely~ charred mass pressed or stirred to a powder by means of a platinum wire or rod hammered flat at the end; the pan should be frequently made to revolve and its contents continually stirred during heating, care being taken, too, to hold it slanting the whole time. The pan should be held in this way over a moderate flame until the ash assumes almost a white colour. As soon as this occurs, the pan should be cooled down and the ash uniformly saturated with a concentrated watery solution of carbonate of ammonia, whereon the vessel is placed in the drying chamber and dried at a temperature of 100 Deg. C. The contents of the pan are then heated again very cautiously over the Bunsen flame, care being taken that the bottom of the vessel is only allowed to become red-hot very gradually and to remain so for a very short time; the pan is then covered up and transferred to the dessicator to be cooled, and, on the completion of this process, its weight determined. After repeating the saturating process with the solution of carbonate of ammonia, drying and heating for a short time as previously described, the accuracy of the weight first obtained is again tested. 3. ~Estimation of silicic acid in the ash~: When examining cocoa powders and chocolate mass, the determination of the silicic acid content of the ash is sometimes a necessity, as this facilitates the detection of any shells which may have been added.[166] The ash ~of the cacao bean contains~ only between 0·25 and 1·0 percent of silicic acid, while that of the shell shows on analysis as much as 9 percent; it must, however, be taken into consideration that an unusually high value for silicic acid in the finished powder might be caused by impurities in the chemical or other agents used to effect the disintegration of the cacao. The signs of the presence of an extraordinary quantity of silicic acid are, according to C. R. Fresenius (Introduction to quantitative analysis)[167] a higher percentage of the ash itself than usual, and the quantity of ash used for the test should not be too small; it should further be remembered that certain cacao preparations, such as, for instance, the Dutch cocoa powders, contain large quantities of carbonic mineral matter, and the special treatment explained by Fresenius when dealing with such preparations separately should be applied.