352 MR. T. CARNELLEY ON A COLOR1METRIC 



(d) 120 cub. cent. ( = 0*99 milligr. Fe) of the original 

 solution taken and diluted to 1 litre. 



.*. 1 cub. cent. = 0*00099 milligr. Fe. 



c. c. nigr. 



200 of this solution taken, =0*1981 

 i*8 required,. =o*i8oj 



.*. the solution contained . 0*900 Fe. 

 Calculated . . . ' . . 0*990 „ 



Difference =—0*090 



A large number of experiments were made in this way, 

 the results of which are given on p. 353. 



In order also to test the effect which the presence of 

 different salts has on this method, four series of experi- 

 ments were made by adding known weights of the following 

 salts to 1 litre of the ammonio-ferrous sulphate solution. 



(A) Calcium sulphate, magnesium sulphate, ammonium 

 chloride, sodium chloride, and potassium carbonate, in all 

 i*6 grm. 



(B) Ditto, in all 0*9 grm. 



(C) Magnesium sulphate, ammonium chloride, potas- 

 sium carbonate, sodium chloride, and calcium chloride, in 

 all 0*8 grm. 



(D) Potassium nitrate 0*4 grm. 



The solutions thus obtained were oxidized with per- 

 manganate and sulphuric acid, diluted to one litre, and the 

 iron estimated as previously described. The results ob- 

 tained are given below, the letters attached denoting to 

 which of the preceding series they severally belong ; and 

 from them it will be seen that the presence of these salts 

 has little or no effect. 



It was also found that neutral orgauic matter is not 

 detrimental to the method. 



