FOOTNOTES:
[64] When chromium is present some of the iron may escape precipitation but it can be recovered from the solution by means of ammonic sulphide.
(1) 10FeSO4 + 2KMnO4 + 8H2SO4 = 5Fe2(SO4)3 + 2MnSO4 + K2SO4 + 8H2O. (2) 6FeCl2 + K2Cr2O7 + 14HCl = 3Fe2Cl6 + Cr2Cl6 + 2KCl + 7H2O.
(1) Fe2Cl6 + SnCl2 = 2FeCl2 + SnCl4.
(2) Fe2Cl6 + SH2 = 2FeCl2 + 2HCl + S.
(3) Fe2Cl6 + Na2SO3 + H2O = 2FeCl2 + Na2SO4 + 2HCl.
(4) Fe2Cl6 + Zn = 2FeCl2 + ZnCl2.
[67] 20 grams of stannous chloride and 20 c.c. of dilute hydrochloric acid are diluted to one litre.
[68] The maximum reducing effect of zinc is obtained by exposing as large a surface as possible of the metal in a hot concentrated solution containing but little free acid (Thorpe).
[69] About 5 inches in diameter.
[70] 61: 60:: 59: 58.13.
The iron in the ore is, then, the same in amount as that in 58.13 c.c. of the ferric chloride solution; and since 100 c.c. of the latter contain 1 gram of iron, 58.13 c.c. of the same contains 0.5813 gram of iron; and, further, if 1 gram of ore carries this amount of iron, 100 grams of ore will obviously give 58.13 grams of iron.
[71] These compounds are Ni2As and Co2As.
[72] With large quantities of iron the ferric precipitate should be re-dissolved and re-precipitated. The filtrate must be added to the original filtrate.
[73]
4KCy + NiSO4 = K2NiCy4 + K2SO4
2KCy + AgNO3 = KAgCy2 + KNO3
∴ 2AgNO3 = Ni
[74] Zn + H2SO4 = H2 + ZnSO4.
[75] These 104 c.c. are equivalent to 100 c.c. of dry air at 0° C. and 760 mm.