Oherhelman — Pentavalent Vanadium. 



533 



titative tests indicate that the reduction is not complete and 

 that the addition of cuprous iodide to solution charged with a 

 sufficient amount of the copper sulphate is without apparent 

 effect. The experiments of Table II show the effects due to 

 variation in the amount of the catalyzer under conditions other- 

 wise similar. 



Table II. 



Reduction in Presence of an Excess of Thio sulphate amounting to 

 2cm3_5cm3 f the n/10 Solution in a Volume o/400 cm3 . 



V 2 5 



v,o 5 



HC1 



CuSO*. 



5H 2 



KI 



Volum 



taken 



found 



(320 











grm. 



grm. 



cm 3 



mgrm. 



grm. 



cm 3 



0-1583 



0-1560 



1-5 





* 



0*45 



400 



0-1583 



0*1555 



1-5 



-- 



* 



0-45 



400 



0-1955 



0-1942 



1-5 



3 



* 



0-45 



400 



0-1955 



0-1950 



1-5 



5 



* 



0-45 



400 



0-1955 



0-1952 



1-5 



7 



* 



0-45 



400 



0-1955 



0-1957 



1-5 



8 



* 



0-45 



400 



0*1955 



0-1958 



1-5 



8 



* 



0-45 



400 



0-0977 



0-0985 



1-5 



8 



* 



0-45 



400 



0-0977 



0-0985 



1-5 



8 



* 



0-45 



400 



0*0977 



0-0983 



1-5 



8 



* 



0-45 



400 



0-1955 



0-1966 



1-5 



10 



* 



0-45 



400 



0-1955 



0-1957 



1-5 



5 





0-4 + 



400 



0-1955 



0-1957 



1-5 



5 





0-4 -f 



400 



0-1955 



0-1957 



1-5 



5 





0-4 + 



400 



0-1955 



0-1955 



1-5 



5 





0-4 + 



400 



0-0977 



00980 



1-5 



5 





0*4 + 



400 



0-0977 



0-0979 



1-5 



5 





0-4 + 



400 



0-0977 



0-0980 



1-5 



5 





0-4 + 



400 



* Cnprous iodide also present in suspension. 



The results obtained are below the theory when cuprous 

 iodide was the only catalyzer, fairly good when cupric sulphate 

 was also present in amounts varying from 5 mgrm. to 10 

 mgrm., and very close to theory when cupric sulphate present 

 to the amount of 5 mgrm. was the only catalyzer. The 

 progress of the reduction was, however, rather slow and the 

 expedient of increasing the excess of thiosulphate in order to 

 accelerate the action was tried. At a volume of 400 cm3 , how- 

 ever, l-5 cmJ of the 32 per cent hydrochloric acid will liberate 

 from the equivalent of 15 cmS of N/10 thiosulphate enough 

 sulphur dioxide to be recognized by the odor. In the follow- 

 ing experiments, therefore, the total volume of the solution 

 was doubled, with corresponding increase in the concentration 



