2:^4 THoMAS-SLAf; OK F.ASIO CINDER. 



THOMAS-SLAG OR BASIC CINDER. 

 By Dr A. ]\ Aitken. ■ 



In the precetling volume of the Tixinsitctiom^, pp. 245-253, an 

 account was given of an experiment made to show the vahie of 

 having insoluble manures ground to the finest possible flour. 

 It was shown that the whole success of mineral phosphates as a 

 manure depended upon their fineness, and it did not very much 

 matter what was the kind of phosphate, so long as it Avas fincl}' 

 ground. Among the manures tested was what was called basic 

 cinder or dag, and which is now being sold under the name of 

 sldfi phoi<p]iat-meol. It is known on the Continent chiefly 

 under the name of Thomas-slag, after the name of one of its 

 inventors. This last name is a specific one, not likely to be 

 giveji to any other substance, and it would be well if all the" 

 other names were now dropped, and this one adhered to, so 

 that farmers may not be confused by a number of names so. 

 different as to seem to apply to different substances, and this is; 

 all the more desirable since it seems that other kinds of slag 

 meal are being sold that are not the true Thomas-slag. 



The substance secured by me for experiment was of exceeding 

 fineness, the whole being able to pass through a wire-cloth 

 sieve of 150 wires per lineal inch, or 22,500 holes per square* 

 inch, and the result of the experiment showed that Thomas 

 slag when applied in that state to turnip crops was as good a 

 manure as superphosphate. 



As this is now the cheapest kind of phosphate in the market, 

 and as it is being widely advertised, it is creating a considerable 

 amount of interest, and on all sides the questions are being^ 

 asked — What is it ( How is it got ? What is it good for ^ 

 How should it be applied .'' Is it an economical stuff to use ? . 



Thomas-slag is a substance formed as a bye-product in the 

 manufacture of steel from pig-iron, by the "basic" or " Thomas- 

 Gilchrist " process. Steel is chiefiy a compound of iron and 

 carbon. It may be made from pig-iron, which also is a compound 

 of iron and carbon, but containing a larger proportion of the 

 latter element than exists in steel. In order to convert pig 

 iron into steel, a portion of the carbon must be burned away, 

 that is to say, oxidised at a very high temperature. Besides 

 carbon, there are various impurities in pig-iron that have to 

 be got rid of, and one of these is phosphorus. Some kinds of 

 pig-iron, according to the ironstone from which they ai'e foraned, 

 and notably that made from Cleveland ironstone, contain so much 

 phosphorus as to render them imfit for making steel of good 

 (juality. On account of the difficulty of getting rid of this 

 impurity, only the purer kinds of pig-iron could formerly be 



