382 Gooch and Hodge — Detection and Separation of 



The second was made on a like quantity of permanganate 

 also in a porcelain mortar. The portion rendered insoluble 

 was dissolved in hydrochloric acid and estimated as Mn 3 4 



Quantity obtained -0136 



showing that 28*25 mgs. of permanganate had been reduced 

 to JVIn0 2 



The same quantity of permanganate treated in the same way 

 in an agate mortar gave only '0030 MnO„ owing to the less 

 efficiency of the mortar. 



The reductions in the case of these last two substances are 

 exothermic, they however do not take place spontaneously, but 

 require the aid of an exterior force — this aid is supplied by 

 shearing stress. 



In these three papers a large number of reactions have been 

 described in which mechanical energy has been transformed 

 into chemism. The number might be extended, but in prac- 

 tice is necessarily limited to those cases in which a perfect sepa- 

 ration can be made between the original substances and the 

 altered product. 



Art. XLIV. — The Detection and Separation of Arsenic asso- 

 ciated imth Antimony and Tin; by F. A. Gooch and 

 13. Hodge. 



[Contributions from the Kent Chemical Laboratory of Yale College — XXIX.] 



Upon the well known fact that hot strong hydrochloric 

 acid is capable of dissolving the sulphides of antimony and 

 tin while exerting solvent action to a very slight degree upon 

 arsenious sulphide is based the simplest and most rapid method 

 in common use for the separation of arsenic from antimony 

 and tin. Unfortunately, however, the forcible treatment 

 necessary to bring about the solution of large amounts of anti- 

 mony is sufficient* to dissolve small quantities of arsenious 

 sulphide, so that for the purposes of general analysis the 

 method is inadequate. Koehlerf has shown that only the 

 arsenic is precipitated, and that very completely, when hydro- 

 gen sulphide acts upon the solution of arsenious and antimo- 

 nious salts in hydrochloric acid of 20 per cent strength, but 



* Rose-Finkener. Anal. Chem., ii, 423. 

 f Zeit. fur Anal. Chem, xxix, 192. 



