Studies on Alloys 
121 
letting d represent the iron value of the solution and the anti- 
mony value : 
55.9 X 10 : 120. 1 X 5 : X. 
Whence 
X = d X 1.075. 
III. Sodl um thiosulphate. Make the solution 'with about 
19 grams of the crystallized salt per liter. Such a solution v^as 
standardized against copper sulphate, the copper content of which 
had been very accurately ascertained in connection with other 
laboratory work. The weighed amounts of the copper sulphate 
were dissolved in about 200 cc. of water. To this was added 5 cc. 
of ammonium acetate solution and 5 cc. of dilute acetic acid. 
Then were added about ten times the copper weight of potassium 
iodide crystals and the mixture stirred. The liberated iodine was 
titrated with the thiosulphate solution nearly to the end, when a 
few cubic centimeters of clear starch solution were added and the 
titration finished. This standard solution was used only for the 
purpose of standardizing the iodine solution and titrating back 
against the iodine solution during the estimations. The iodine 
value of the thiosulphate solution was calculated as follows from 
the reaction equation: 
2CUSO4 + 4KI = 2I + CU2I2 + 2K2SO4 
Weight of copper sulphate taken = .xxxx {a) 
Percentage of copper present in the sulphate = .xxxx (b) 
Weight of pure copper present = {a) X {h) = .xxxx (c) 
Weight iodine equivalent to copper ^ (c) X = .xxxx{d) 
Volume NagSgOa used = .xxxx {e) 
I cc. thiosulphate = (d) (e) = .xxxxxg. I. 
IV. Iodine. About 18 grams of pure potassium iodide were 
dissolved in 250 cc. of water and 13 grams of iodine were dissolved 
in the resulting solution. When solution was complete the whole 
was diluted to a liter. This iodine solution was titrated against 
measured volumes of the standard thiosulphate solution using a 
clear solution of starch as an indicator in just the way described 
above. The standard values were calculated as below: 
I cc. of thiosulphate in grams of iodine (as above) = .xxxx (a) 
I cc. of thiosulphate in cubic centimeters of I sol. = ,xxxx (h) 
I cc. of the iodine solution in grams of iodine(a = .xxxx (c) 
