Prof. Chapman on the Assaying of Coals hy the Blowpipe. 435 



the method first pointed out by Von Kobell. A fragment placed 

 in a solution of sulphate of copper (blue vitriol) in contact with 

 a strip of zinc will become quickly coated with a deposit of me- 

 tallic copper, a phsenomenon not exhibited in the case of common 

 coal. Deducting ash and moisture, true anthracites present, as 

 a mean,the following composition :— Carbon, 92|; Hydrogen, 31; 

 Oxygen (with trace of nitrogen), 4. All yield an amount of coke 

 equal to or exceeding 89 per cent. The coke is frequently pul- 

 verulent, never agglutinated. 



The comportment of anthracite before the blowpipe has not 

 hitherto been given in detail. It is as follows : — pe?- se, the assay 

 quickly loses its metallic briUiaucy. After continued ignition, 

 small white specks of ash appear on its edges. In borax it dis- 

 solves very slowly, with constant escape of bubbles. It is not 

 attacked by salt of phosphorus ; the assay works to the top of 

 the bead and slowly burns away. In carbonate of soda it effer- 

 vesces, scintillates, and turns rapidly in the bead, and the soda 

 is gradually absorbed. In the bulb-tube a little water is always 

 given off, but without any trace of bituminous matter. 



As regards their geological position, the true anthracites be- 

 long chiefly to the middle portion of the palaeozoic series, below 

 the carboniferous formation; or otherwise they constitute the 

 under portion of the coal-measures. Frequently also anthracites 

 occur in the vicinity of erupted rocks, and amongst metamorphic 

 strata, as manifest alterations of ordinary coal. 



2. Anthracitic Coals. — These are often confounded with the 

 true anthracites, into which indeed, as already stated, they gra- 

 dually merge. Normally they differ from the true anthracites 

 in being non-conductors of electricity, in burning more easily 

 and with a very evident yellow flame, in yielding a small quan- 

 tity of bituminous matter when heated in a tube closed at one 

 end, and in furnishing an amount of coke below 80 per cent. 

 The coke is also in general more or less agglutinated, although 

 it never presents the fused, mammillated appearance of that ob- 

 tained from caking coal. The mean composition (ash and 

 moisture deducted) may be represented as follows: — Carbon,89i; 

 Hydrogen, 5; Oxygen (with traceof nitrogen), 5i: orCarbon,89; 

 Hydrogen, 5 ; Oxygen (with trace of nitrogen),"" 6. 



3. Caking Coals. — These are often termed technically "fat 

 coals." They constitute the type-series of the coals, properly 

 80 called. All yield a fused and mammillated coke, varying in 

 amount from G5 to 70 per cent. Spec. grav. =1-27 to 1-32. 

 Commonly mixed with thin layers of strongly soiling "mineral 

 charcoal" or fibrous anthracite. Mean composition (ash and 

 moisture excluded) :— Carbon, 87-9; Hydrogen, 5-1; Oxygen 

 (with nitrogen), 70. 



