Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

SODIUM HYDRAZOATE. Ill

roughly measured. Shake the seven bottles in a shaking-machine

for about ten hours at as constant a temperature as possible. Let

settle, and titrate 100 c.c. of the clear solution from each of bottles

1, 2, and 3, with thiosulphate; 50 c.c. each from bottles 4 and 5;

25 c.c. from bottle 6; and 20 c.c. from bottle 7. From these

results the molecular concentrations of iodine, D and B, are

obtained; the value of A is the original concentration of the

potassium iodide solution used. If these values are introduced

in the above mass-law equation, a constant value for K should be

obtained, which at 20° is about 0.0013.

Experiments with more concentrated potassium iodide solutions
show an increase in the values of the constant; this indicates the

presence of higher poly-iodides.

71. Rubidium Iodine Tetrachloride, Rb[ICl 4 ]; Potassium Iodine
    Tetracbloride, K[IC1 4 ]; Rubidium Tri-iodide, Rbl 3.

Dissolve 2.5 g. of rubidium chloride in 7.5 c.c. of water and sus-
pend 2.7 g. of iodine in the solution. On passing chlorine into this

mixture large, beautiful, orange-red crystals of rubidium iodine

tetrachloride are obtained. The iodine dissolves during the action

with a slight liberation of heat, and later the new salt separates in
large plates which increase in quantity after several hours standing

in the ice-chest. Drain the crystals without washing and allow

them to dry for an hour in a vacuum desiccator over sulphuric

acid. Too long drying causes decomposition. Yield about 5 g.

A corresponding potassium iodine tetrachloride is formed by

triturating 1 g. of potassium iodate with a little concentrated

hydrochloric acid in a mortar. Chlorine is liberated as the iodine

of the iodate is reduced. Continue the trituration, adding small

portions of concentrated hydrochloric acid from time to time, until

finally there is no further evolution of chlorine. This requires

about 5 c.c. of acid. A paste of dull-yellow' crystalline needles

remains. Filter, drain with suction and wash with a little concen-

trated hydrochloric acid. On standing, the salt slowly decomposes.

The behavior of this salt with ether, which dissolves out iodine

trichloride and leaves behind white potassium chloride, would

indicate that it may have the constitution K[C1 • IC1 3 ].

Rubidium Tri-iodide, Rbl 3 , is obtained by crystallization from

a warm solution of iodine in rubidium iodide. Neutralize a