OF ARTS AND SCIENCES. 53 



I. In a cold solution of VO.^ in SO^Hj three successive portions 

 of 200 cc. each required 4.G2 cc, 4.64 cc, and 4.63 cc. of 

 liypermaiiganate solution. 

 II. At 53° C. 200 cc. as before required 4.62 cc. 



III. At 62° C. 200 cc. required 4.66 cc. Process rather more rapid. 



IV. At 70° C. " " 4.66 cc. " " " 



V. At 80° C. " " 4.65 cc. Color vanished instantly. 



VI. At 100° C. " " 4.64 cc. " " 



The following analyses will show the effect of reducing by hydric 

 sulphide, as compared with reduction by sulphurous acid. In an acid 

 sodic vanadate : — 



gave 0.0406 gr. Y,0^ = 44.67% with H^S 

 " 0.0607 gr. " =43.92% " 



« 0.0692 gr. " =44.90% « 



" 0.0696 gr. « =42.99% with SO3H2 

 " 0.0659 gr. " =43.01% " 



When hydric sulphide is used as a reducing agent, it often happens 

 that the filtrate on evaporation deposits more sulphur. In titrating 

 with hypermanganate, the final color reaction must be permanent for 

 ten to fifteen minutes at least. As usual, the amount of hyperman- 

 ganate required to color an equal volume of water and dilute sulphuric 

 acid must be determined, and the proper correction applied. 



In my paper on the vanadio-molybdates I have given another 

 method of determining vanadium based upon the fact that a ferrous 

 salt readily reduces vanadic pentoxide in the presence of free chlor- 

 hydric acid. I have since found that this method is not new, but was 

 proposed and tested by Otto Lindemann * some years since. 



1 : 1 Ammonic Phospho-vanadate. — When any amnionic vanadate 

 is dissolved with an excess of ammonic phosphate, and nitric acid is 

 cautiously added in small quantities at a time, a deep orange-red solu- 

 tion is obtained, which on heating becomes colorless, but which on 

 evaporation to a small volume yields beautiful bright yellow granular 

 crystals. These are to be carefully washed with cold water, in which 

 they are not very soluble. The solution has at first a fine yellow 

 color, but on continued dilution with water passes through the changes 

 in color which have already been described. In this salt, 



* Ueber die quantitative Bestimmung des Vanadins. Inaugural Dissertation 

 von Otto Lindemann. Jena, 1879. 



