30 Organic Acids in the Examination of Minerals. 



usual glass bottle of liquid hydrochloric acid, and the addition 

 of potassium nitrite to the usual list of dry reagents contained 

 in portable blow-pipe cases. Since citric acid solution decom- 

 poses potassium nitrite in the cold, we can carry nitric acid 

 practically in a solid form 5 hydropotassium sulphate, already 

 in use, furnishes sulphuric acid in a solid state j and it only 

 remains, therefore, to provide for hydrochloric acid. Our 

 experiments have as yet failed to solve this problem directly ; 

 ammonium, sodium, and potassium chlorides appear to resist 

 the action of the organic acids. Iodiue, on the other hand, 

 while much less powerful than chlorine, possesses similar 

 properties, and will form a valuable addition to the list of dry 

 reagents ; in aqueous solution it attacks many sulphides, and 

 gives rise to characteristic phenomena. Iodine water was 

 employed as early as 1858, by Professor Henry Wurtz, to sep- 

 arate pyrrhotite from pyritej* but he did not extend its use 

 to the determination of minerals, a question which we are now 

 engaged in studying, and which has already yielded very 

 interesting results. 



Citric acid, potassium nitrite, and iodine, then, added to 

 the reagents in common use, — borax, sodium-carbonate, 

 potassium cyanide, ammonio-sodium phosphate, test-lead, tin, 

 and an assortment of test-papers, inclnding acetate of lead 

 paper, together with as many of the solid reagents used in 

 solutions as space will admit, would complete the outfit of 

 dry reagents for wet analysis and for blow-piping. 



A pocket case, made of lacquered tin, 20 cm. long, 5 

 cm. wide, and 2.3 cm. deep, containing pasteboard boxes 

 (pill-boxes) of citric acid, potassium nitrate, dried borax, and 

 sodium carbonate, together with a few simple requisites for 

 blow-pipe work, has been used by the writer in short mineral- 

 ogical excursions with great satisfaction. To carry on the 

 examination with solutions, we are also provided with a paste- 

 board case, cylindrical in form, 14 cm. long, containing five 

 stout test-tubes, fitting one within another, like a nest of 

 beakers; the interior tube is open at both ends, a cork inserted 



* American Journal of Science, (2) xxvi, 190. 



