Chemistry and Physics. 163 



bright silvery sheen. It contains a good deal of ferric chloride 

 and is rapidly crumbling. On polishing down one of the sides, 

 the Widmanstatten figures (coarse) came out very plainly, no 

 etching being necessary. 

 The analysis gave : 



Fe 90-54, CI 0-35, SiO„ 0-04, P 0-13, Co 0*94, Ni 7-70 = 99-70 

 University of North Carolina, May, 1890. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Nature of Solutions. — Pickering has continued his 

 investigations on the nature of solutions and now gives the re- 

 sults as deduced from the freezing point of sulphuric acid solu- 

 tions. The following are his conclusions: "The freezing points 

 of solutions of sulphuric acid form four separate figures, each of 

 which represents the crystallization of a different substance. In 

 the case where water crystallizes out, the figure consists of a 

 single branch curve, whereas in the cases where the tetrahydrate 

 the monohydrate and anhydrous sulphuric acid crystallize out 

 each figure consists of two curves rising up and meeting at points 

 corresponding with the composition of the substance crystallizing 

 in each case respectively. The tetrahydrate as a solid, is a new 

 hydrate melting at —25°, its existence in solution having been pre- 

 viously established. Irregularities and sudden changes of curva- 

 ture are found in the figures. These changes occur at the same 

 points as those noticed in the case of the densities, heat-capacity, 

 heat of dissolution, expansion by heat, and electric conductivity.* 

 Of the seventeen hydrates indicated by the last-named proper- 

 ties, everyone has received further confirmation from the present 

 work where such confirmation was possible (in thirteen cases) ; 

 in addition to which, three others have been recognized (two of 

 which were, however, suggested by the previous work), thus 

 raising the total to twenty. Sudden changes at H 2 S0 4 and at 

 about 36H 2 S0 4 S0 3 have also been established. The freezing 

 point diagram shows that the existence of a definite hydrate may 

 be marked by an indubitable change of curvature at the point 

 corresponding to its composition (e. g., H 2 S0 4 (H 2 0) 4 and H„SO ). 

 Many of the changes are sufficiently marked to be evident with- 

 out the aid of differentiation. The constituent portions of the 

 various figures are probably not parabolic. The changes at the 

 extreme end of the water-curves, with solutions containing less 

 than H 2 S0 4 to 100 H 2 0, are of considerable magnitude. The 

 figure here instead of being made up of one straight line, is made 

 up of several straight lines, the last change observed occurring 



* Noticed in the May number of this Journal. 



