=31. German Ash Method.=—The method pursued at the Halle Station for securing the percentage of ash in a sample is as follows:[16] Five grams of the air-dried sample are incinerated in a platinum dish and the ash ignited until it has assumed a white, or at least a bright gray tint. As soon as combustible gases are emitted at the beginning of the incineration they are ignited and allowed to burn as long as possible. It is advisable to hasten the oxidation by stirring the mass with a piece of platinum wire. If the ash should become agglomerated, as sometimes happens with rich food materials, it must be separated by attrition. The ash, when cooled on a desiccator, is to be weighed. When great exactness is required, it is advised, as set forth in a former paragraph, to first carbonize the mass and then extract the soluble ash with hot water before completing the oxidation. When the latter is complete and the dish cooled the aqueous extract is added, evaporated to dryness and the incineration completed. =32. Courtonne’s Muffle.=—The ordinary arrangement of a muffle, as in assaying, may be conveniently used in incineration. A special muffle arrangement has been prepared by Courtonne which not only permits of the burning of a large number of samples at once, but also effects a considerable saving in gas. The muffle as shown in Fig. 17, is made in two stages, and the floor projects in front of the furnace, forming a convenient hearth. The incineration is commenced on the upper stage, where the temperature is low, and finished on the lower one at a higher heat. The furnace is so arranged as to permit the flame of the burning gas to entirely surround the muffle. The draft and temperature within the muffle are controlled by the fire-clay door shown resting on the table. TREATMENT WITH SOLVENTS. =33. Object Of Treatment.=—The next step, in the analytical work, after sampling, drying, and incinerating, is the treatment of the sample with solvents. The object of this work is to separate the material under examination into distinct classes of bodies distinguished from each other by their solubilities. It is not the purpose of this section to describe the various bodies which may be separated in this way, especially from vegetable products. For this description the reader may consult the standard works on plant analysis.[17]