=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the organic matter will burn of its own accord after it is once ignited, and during this combustion the lamp should be withdrawn.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.