82 , REPORT — 1869. 



Report of the Committee on the Chemical Nature of Cast Iron. The 

 Committee consists o/F. A. Abel, F.R.S., D. Yorbes, F.R.S., and A. 

 Matthiessen, F.R.S. 



The Committee have to report that, during the past year, some material 

 progress has heen made in this research. They entrusted the preparation 

 of the pure iron to Mr. Matthiesscn, who carried out this part of the inves- 

 tigation in conjunction with Mr. Prus Szczepanowski. From a series of ex- 

 periments, which are detailed in the Appendix, pure iron appears to be ob- 

 tainable in considerable quantities, and wo hope, if the Committee be re- 

 appointed, that next year a great deal of valuable information will be obtained 

 on the chemical nature and physical properties of pure iron and its alloys. 

 The iron obtained by the process described in the Appendix is almost abso- 

 lutely pure, containing only a minute trace of sulphur. According to an 

 analysis made by Prof. Abel, the iron contained, in a hundred parts, only 

 0-00025 part of sulphur. In another analysis, the amount of sulphur found 

 by Mr. Prus Szczepanowski amounted to 0-0007 per cent.* Phosphorus and 

 silicon were carefully tested for by both analysts, and found to be entirely 

 absent. 



"With regard to the physical properties of pure iron, owing to the -want of 

 time, nothing as yet has been accm-ately determined. It appears, however, 

 that many of the physical properties of the pure metal differ considerably 

 from those of the commercial. 



APPENDIX. 



On the Preparation of Pv/re Iron. By A. Matthxessen, F.R.S. , and S. Pktts 



Szczepanowski. 



After numerous trials, the general outline of which was given in the 

 lleport of last year, the following method was found to yield nearly abso- 

 lutely pure iron, in quantities sufficient for the purpose of this research. 

 Pure dried ferrous sulphate and piire dried sodium sulphate are mixed in 

 nearly equal proportions, and introduced gradually into a red-hot platinum 

 crucible. The mass is kept in fusion until the evolution of sulphurous acid 

 gas ceases. The crucible is then allowed to cool, and the fused mass ex- 

 tracted with water. If the heat be properly regulated, the whole of the 

 iron is left as a very fine crystalline oxide. This oxide is thoroughly washed 

 by decantation to remove every trace of the sodium sulphate, and, after 

 being dried, is reduced by hydrogen in a platinum crucible ; the spongj'^ iron 

 thus obtained is then pressed into solid buttons and melted in lime crucibles 

 Avith the oxyhydrogen-blowpipe. 



Before proceeding further, it will be as well to mention the precautions 

 observed in obtaining the raw material in the purest state. The commer- 

 cial pure ferrous sulphate was freed from every trace of copper by leading 

 sulphuretted hydrogen through the warm acetic acid solution. After filtra- 

 tion, the ferrous sulphate was twice recrystallizcd and dried, first in a water- 

 bath, then in an air-bath. The commercial crystallized sodium sulphate was 

 recrystallizcd several times to get rid of the last traces of chloride of sodium, 

 and then heated on a water-bath to melt the crystals. As is well known, 

 anhydrous sodium svdphate separates out from this solution, which was 

 scooped out from time to time, dried on an air-bath, and powdered. The 

 purification of the sodium sulphate from chloride of sodium was found to be 

 necessary, owing to the fact that, when fusions were made with sodium sul- 

 * The amount of substance taken for eacli analysis was about 30 grammes. 



