THE MANUKIAL VALUE OF SOOT.

Daily Southern Cross, Volume XXIV, Issue 3355, 17 April 1868, Page 4

THE MANUKIAL VALUE OF SOOT.

A correspondent has had, through our agency, a sample of soot analysed for him, and finds that it contains 2.45 per cent, of ammonia, and has a money value (according to analysis) of £1 10s. per ton. The circumstance leads us to m»ke a few remarks upon the fertilising value of this substance, which may prove interesting to our readers. Soot is one of the products of the imperfect combustion of carbonaceous substances used as sources of artificial light and heat. It consists essentially of carbon and charcoal, in a state of minute division ; but it also includes a great variety of substances, such as sulphate of ammonia, sulphite of ammonia, sal ammoniac, sulphate of lime, common salt, f ulignic acid, earthy salts, and several complex organic bodies. In some (thoroughly dried) samples the amount of charcoal is found to be 98 per cent., in others only 80. This great variety depends upon the nature of the substances from which the samples (are derived. It, therefore, frequently happens that the fertilising value of this article is almost nil, whilst in other cases, as in the one quoted, it is very high. The Boot derived from the imperfect combustion of coke, wood charcoal, *nthr»cite, culm, or Kilkenny (blind) coal is, generally speaking, perfectly worthless for manurial purposes ; on the other hand, Newcastle coal yields a very valuable kind o£ soot, and a still better variety if obtained from the Scotch cannel or candle coal. A3 the latter is, owing to its large per-centage of bitumen, more or less employed in the manufacture of illuminating gas, the agriculturist who uses soot may be pretty sure that all he may obtain from gas-works is of good quality. Wood and turf yield soot of a very low specific gravity or density, but, »s a rule, of tolerable manurial power. There is usually a large proportion of f ulignic and other acids of vegetable origin in wood and turf soot, and it safer to use it in a compost form. Although carbon constitutes nearly the whole weight of soot, this ingredient possesses little, if any, manurial value. The alkaline and earthy salts in soot are, so far as they go, useful ; but in very few samples of soot do they increase the value of the article, by even so much as Is. 6d. per ton. The only really useful constituent of soot is ammonia. When coal or wood containing nitrogen is burned or charred, the nitrogen unites with the hydrogen (which is always present when nitrogen is an ingredient of the fuel), and forms the gas termed ammonia. Soot, like other varieties of charcoal, possesses remarkable absorbent power over gases, and therefore retains in its pores a portion of the ammonia which escapes from the burning fuel. Sulphur is a usual ingredient of coal, and during the combuscion of it unites with the atmospheric oxygen and forms sulphurous acid, which, beiDg volatile, flies off in union with some, perhaps all, of the ammonia, f orming the sulphite of that alkali. A very large proportion, sometimes indeed the whole, of the ammonia contained in soot exists in the form of sulphite ; but it is also very often in union with various organic and semi-organic acids developed during the combustion of the fuel. The proportion of ammonia in soot varies from 0. 5 to 7 per cent., but the average (from coal) is about 3 per cent. Soot is applied to almost every kind of crop, but is most commonly employed as a top-dressing for grass land. When used for this purpose in spring it is said to impart a disagreeable flavour to the butter of the cows fed upon the grass manured by it. However, our own experience does not verify this assertion. It has been used as a top-dressing for wheat with excellent results ; and applied to potatoes it is found to materially promote the growth of that crop. Where soot can be obtained cheaply and of good quality it might be used as a very economic substitute for Peruvian guano or sulphate of ammonia, in admixture with superphosphate of lime. Such a compound would be well adapted for root crops, more especially in the case of stiff clays. The quality of soot may be roughly estimated by mixing an ounce of it with an equal quantity of recently-slaked and well-moiatened quick-lime ; the more pungent the odour the larger will be the proportion of ammonia, and the more valuable will be the soot.— Irish Farmers 1 Gazette.