229. Fertilizing Value of Ashes.—Primarily, the fertilizing value of wood-ashes depends on the quantity of plant food which they contain. With the exception of potash and phosphoric acid, however, the constituents of wood-ashes have little, if any, commercial value. The beneficial effects following the application of ashes, however, are greater than would be produced by the same quantities of matter added in a purely manurial state. The organic origin of these materials in the ash has caused them to be presented to the plant in a form peculiarly suited for absorption. Land treated generally with wood-ashes becomes more amenable to culture, is readily kept in good tilth, and thus retains moisture in dry seasons and permits of easy drainage in wet. These effects are probably due to the lime content of the ash, a property moreover favorable to nitrification and adapted to correcting acidity. Injurious iron salts, which are sometimes found in wet and sour lands, are precipitated by the ash and rendered innocuous or even beneficial. A good wood-ash fertilizer therefore is worth more than would be indicated by its commercial value calculated in the usual way.
230. Molasses from Sugar-Beets.—The residual molasses resulting after the extraction of all the crystallizable sugar in beet-sugar manufacture is very rich in potash. The molasses contains from ten to fifteen per cent of ash.
The composition of the ash varies greatly in the content of potash as well as of the other constituents.[191] The content of potassium carbonate varies from twenty-two to fifty-five per cent and, in addition to this, some potassium sulfate and chlorid are usually present.
The following figures give the composition of a good quality of beet-molasses ash:
| Potassium | carbonate | 45.30 | per cent | |
| Sodium | “ | 13.86 | “ | |
| Potassium | chlorid | 22.40 | “ | |
| “ | sulfate | 8.00 | “ | |
| Silica, lime, alumina, water, phosphoric | ||||
| acid, and undetermined | 15.82 | “ | ||
Thus, in 100 parts of such an ash over three-quarters are potash salts. The molasses may be applied directly to the soil or diluted and sprayed over the fields.
231. Residue of Wineries.—The pomace of grapes after being pressed or fermented for wine production contains considerable quantities of potash as crude argol or acid potassium tartrate. This material can be applied directly to the soil or first burned, when its potash will be secured in the form of carbonate.
The use of the winery refuse for fertilizing purposes has not assumed any commercial importance in this country.
232. Destruction of Organic Matter by Direct Ignition.—The simplest and most direct method for destroying organic matter is by direct ignition. The incineration may be conducted in the open air or in a muffle and the temperature should be as low as possible. In no case should a low red heat be exceeded. By reason of the moderate draft produced in a muffle and the more even heat which can be maintained this method of burning is to be preferred. With the exercise of due care, however, excellent results can be obtained in an open dish or one partly closed with a lid. At first, with many samples, the organic matter will burn of its own accord after it is once ignited, and during this combustion the lamp should be withdrawn. The ignition in most cases should be continued in a platinum dish but should the sample contain any reducible metal capable of injuring the platinum a porcelain vessel should be used. The lamp should give a diffused flame to avoid overheating of any portions of the dish and to secure more uniform combustion. In using a muffle the heat employed should be only great enough to secure combustion and the draft should be so regulated as to avoid loss due to the mechanical deportation of the ash particles.
233. Ignition with Sulfuric Acid.—The favorable action of sulfuric acid in securing a perfect incineration may also be utilized in the preparation of samples containing organic matter for potash determinations. In this case the bases which by direct ignition would be secured as carbonates are obtained as sulfates. In the method adopted by the official chemists it is directed to saturate the sample with sulfuric acid and to ignite in a muffle until all organic matter is destroyed.[192] Afterwards, when cool the ash is moistened with a little hydrochloric acid and warmed, whereby it is the more easily detached from the dish. The potash is then determined by any one of the standard methods. This method has several advantages over the direct ignition. Where any chlorids of the alkalies are present in the ash there is danger of loss of potash from volatilization. This is avoided by the sulfate process. Moreover, there is not so much danger in this method of occluding particles of carbon in the ash.