THE RURAL WORLD.

King Country Chronicle, Volume VI, Issue 478, 29 June 1912, Page 3

THE RURAL WORLD.

WHERE MANURES COME FROM. ORIGIiN OP SOME WIDELY USED FERTILISERS. A little seed may grow into a big tree, and a small thought may prove the germ of a great idea. When Watt, the inventor of trie steam engine, sat meditating before the kitchen fire and observed the lid of the boiling kettle bobbing up and down with the energy of the steam beneath it, he conceived the idea of putting such energy into practical U9e. The steam engine was the outcome of his mediations. In like manner, though perhaps ? n a less striking fashion, stray observations have led to the discovery of some of our most valuable commercial fer ilisers. Probably from very early times *"oad scrapings have been used as a dressing for grass land, especially in limestone districts. Many years ago it was observed that the road scrapings in cartain districts of this country possessed a peculiar virtue in encouraging the growth of clovers and .improving the quality of the herbage of the pastures to which they were applied. This led to a chemical examination of the material used in the construction of the roads, and the discovery that such material was rich in phosphate of lime the value of which was already recognised as a manorial constituent of bones. This material it was the coprolites of Cambridgeshire and Bedfordshire —which was first used and it was this comparatively simple observation which led to the establishment of the extremely important industry of the manufacture of superphosphate. At first the rock was used merely in the ground condition, and then the process of submitting it to the action of strong sulphuric acid or oil of vitirol —which had been previously applied successfully to bones—was applied to the mineral phosphate, the result being markedly to increase its value as manure. Nowadays, the untreated ground phosphate is never used and our own native supplj of coprolites, through not yet completely worked out, is no longer utilised. Mineral phosphatesot varying degrees of richness are found in practically every European country indeed, almost all over the world. For a while the large deposits of rich natural phosphates of Florida and South Carolina held the field, but these have latterly given place to even larger and equally rich deposits in Algeria on the North coast of Africa. The actual source of supply of the mineral phosphate used in the manufacture vi superphosphates at the present day is regulated by the richness in phosphate of lime of the rock and the cost of quarrying and transportation. Large accumulations in various parts of the world are lying unworked because cheaper sources of supply are at present available. Happily, the day seems far distant when the world's supply of mineral phosphate will become exhausted. It seems a far cry from the dung heap to the steelworks, and the latter wuuld seem to be the last place in the world to look lor the substance likely to displace the former for pocket knives, for plates, for building bridges and Dreadnoughts, for safety razors, if you like. Why, yes; but for manure you'd better try the job master's stables ! Yet, unlikely as it may seem one of our most valuable fertilisers, viz., basic slag, is obtained as a by-product in trie manufacture of steel. The writer, though comparativley young can remember quite well this manure first coming into use. Apparently the way in which its value was discovered was quite simple. Everyone who lives in, or has travelled through, iron and steel smelting districts has noticed those ugly black moulds of slag which are dumped down on the nearest bit of waste ground. For a time these heaps accumulated unheeded, ani then it was noticed that on the outide of certain mounds, where the slag crumpled down by the agency of water, air, and frost, a marked effect was observable on the herbage growing near. An examination of the slag led to the discovery that it contained phosphate of lime in considerable, though variable quantity, and the field trials set on foot served to establish its value as a ' manure. Phosphorous occurs naturally , in certain kinds of ironstune. an'.l this, if not got rid of, tends to make ; the steel manufactured from it brittle and liable to snap easily. At a certain stage of the process, therefore, the manufacturer blows steam and air ( through the molten mass. This com- j bines with the phosphorous present, giving phosphoirc acid, which again combines with the lime with which j the vessel or converter is lined, giving . phosobate of lime. Being lighter , than the molten metal the shag rises . to the top and after the metal has ' been run out of the converter at the , bottom, the slag is tipped out and . left to cool, setting into a hard, heavy, , black substance something like basalt. The substance is afterwards ground j by powerful machinery, and is then | ready fur sale. Much the same end is achieved in the ease of basic siag by reducing it to an exceedingly fine state of sub-division as in that of superphosphate by dissolving it with , sulphuric acid. From the purchaser's point of view it is imnortant to notice that it i 3 ' only slag which is made by a particular process of steel conversation, viz., the Thomas Gilchrist process—hence the name, Thomas' Phosphate Powder —-which possesses any value as a manure. Throughout the country large accumulations of slag produced previous to the introduction of this process are to be found. Hence in buying any but the best knuwn or standard brands it is advisable to ; check deliveries by taking samples for analysis. ; Another of our most valuable fertilisers is obtained from coal. It is probably a matter of common know- , lege that sulphate of: ammonia is ob-

tained from the gasworks as a by product from the distillation of coul gas. For a long time this was our main, indeed at. one time our only source of supply, but of recent years an important industry has arisen in the recovery of this material at the coke ovens. The writer recently had the opportunity of seeing one of these plants which had been installed at a collkry in the north of England, aad i)p will attempt to describe the process very briefly. Under the old sytem of burning coke, the coal was thrown into a kind of bee hive shaped brick kiln. It was then set on tire, and burnt in a limited supply of air until the cooking process was complete. The gas of the coal and the whole o 1 " the valuable by products were consumed, the latter being entirely wasted. Under the new system a coke oven is practically a retort, and consists of a narrow rectangular chamber capable of holding nine tons of coal. The ovens are set side by side and between each pair is another narrow chamber where the heat can be applied through the walls of the ovens. On heating, the coal gas, together with other volatile products, such as coal tar, ammonia and pitch are driven off. These are drawn along, pipes to condensers,' where the tarry proiucts are first removed. The coal gas with the ammonia still in it is carried to what is known as the saturator, where the ammonia is brought in contact with sulphuric acid of a given strength. The ammonia combines with the acid and is deposited as a solid, giving the familiar greyish white salt. After the coal gas is carried on, first to a gas holder and finally it is taken back to the heating chambers of the ovens, here it is burnt to give the necessary heat for conducting the process. At the ovens which are inspected every ton of coal used for cooking yielded about 301b of sulphate of ammonia of high purity. In this process not only is a valuable agricultural fertiliser recovered, but th 9 tarry products, which are even more valuable from the commercial point uf view, are also secured; while, as we have already seen, the coal is brought back and burnt in the furnace. Not only so, but the heat produced by thp o'vens is conducted away and used for producing steam. It may be of interest to note that practically the whole of the manure manufactured at this colliery was exported to Japan.—Farmer and Stockbreeder.