r 

 of the Argillaceous Iron-Ore. ' 283 



the quality of the mineral is capable of yielding. Limestone 

 is the only fluxing material which is in constant and systematic 

 use with the iron smelter ; but as the different specimens of 

 this mineral vary extremely in the nature of their constituent 

 parts, it may often be a matter of much moment for him to be 

 able to make a correct assay of the composition of all those 

 which are situated conveniently within his reach. For if he 

 be in the dark regarding their true constitution, he may know 

 well enough the sort of flux which his ore requires, and believe 

 that he exhibits this in the furnace, at the same time that his 

 ignorance of its composition may cause him to offer a different 

 material from that which he intends to use. In order to ascer- 

 tain the constituent parts of a limestone, nothing more is re- 

 quired than to follow out an analysis of precisely the same 

 nature with that which has just been described for ores of iron. 

 This arises from the circumstance, that limestones are of a com- 

 position extremely analogous to that of the argillaceous carbo- 

 nates of iron. It is only necessary to remark, that even in 

 those cases in which the amount of iron which is present in a 

 limestone may be very inconsiderable, it is still advantageous 

 to precipitate it with ammonia in the state of peroxide, before 

 any of the other ingredients are separated. As solvents act 

 more easily upon limestones than upon the iron-ores, the mu- 

 riatic acid which is employed to dissolve the former should be 

 diluted with at least thrice its volume of water. 



Before leaving this subject, we are desirous of shortly ad- 

 verting to the mode of analyzing another very important ma- 

 terial which the smelter is obliged to employ in large quanti- 

 ties, we mean coal. The composition of this mineral varies so 

 much in different strata, that it very much concerns his inte- 

 rest to be able in all cases to appreciate what proportion of a 

 coal is combustible, and what proportion of it consists of earthy 

 ingredients, and also what is the composition of these earthy 

 ingredients. 



In order to determine the first of these points, the amount 

 of combustible matter contained in any coal, the following pro- 

 cess will be found convenient and satisfactory. Reduce the 

 coai to a very fine powder, and weigh out a determinate quan- 

 tity of it, (say from forty to fifty grains.) Put about six or 



