64 C. W. E. POWELL. 



on steel wire and converted into the monohydrated salt by 

 the method of purification adopted, a possible alternative 

 view being that there was sufficient water in the flask to 

 form FeS0 4 + H 2 initially, since in addition to the 2-3% 

 of water found in the acid, a further amount was being 

 continuously formed in the generation of sulphur dioxide 

 gas according to the equation : — 



Fe + 2 H 2 S0 4 = FeS0 4 + SO a + 2 H 2 0, 

 two molecules of water being formed for every one of ferrous 

 sulphate. However this will be again discussed when the 

 respective amountsofS0 2 and hydrogen have been recorded. 



Method of Gas Analysis. 

 The gas evolved was analysed in Hempel's apparatus, 

 using a modified Winkler gas burette. After observing 

 the initial volume and temperature the mixture of gases 

 was passed into a Hempel gas pipette, containing a solution 

 of potassium hydrate, when all the sulphur dioxide was 

 absorbed (as well as any other soluble gases which may 

 have been present in very small quantities). The diminu- 

 tion in volume represented the volume of S0 3 originally 

 present after allowing for the vapour tension of the KOH 

 solution, since the gases at start were dry owing to the 

 dehydrating action of the sulphuric acid used to obtain 

 them. The remaining gas was then passed into a gas 

 pipette filled with a solution of alkaline pyrogallol prepared 

 by mixing together — directly in the gas pipette — 5 grams 

 of pyrogallol dissolved in 15 c.cms. of water and 120 grams 

 of KOH dissolved in 80 c.cms. of water. The gas absorbed 

 by this solution was considered to be atmospheric oxygen, 

 and a corresponding amount of nitrogen calculated on the 

 basis that air contains 21% of oxygen by volume. About 

 16 c.cms. of the oxygen-free gas were then passed into a 

 pipette and mixed with an excess of air, exploded in an 

 explosion pipette and the contraction in volume observed. 



