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

154 ORGANOCOMPLEX COMPOUNDS.

a paper stencil in a printing frame. At the end of the exposure,

only the outlines of the pattern are to be distinguished, but the
print may be developed by placing it for about one minute in a
warm solution of potassium oxalate. Fix the "picture" in dilute
hydrochloric acid, wash it repeatedly with water and then dry it.
If potassium chloroplatinite is used instead of chloroplatinic acid
the picture is developed of itself during the printing, but it should

be fixed as in the preceding case by washing with dilute hydro-

chloric acid and water.

119. Optical Rotation of Uranyl Lsevo-malate.
     Aqueous, not too concentrated, solutions of ordinary malic acid rotate
     the plane of polarized light feebly toward the left. The presence of uranyl
     salts increases the extent of the rotation very considerably, and this is presum-
     ably due to the formation of complex compounds, although such substances
     have not yet been isolated. For this experiment a sensitive polarizing appa-
     ratus with graduations is necessary.

Prepare the following solutions: (I) 1.3 g. of malic acid in 10 c.c.

of water; (II) 4 g. of uranyl nitrate in 10 c.c. of water; (III) 2 g.

of potassium hydroxide in 20 c.c. of water.

First mix 1 c.c. of (I) and 2 c.c. of (III) and dilute to 20 c.c.

Next prepare the same mixture of solutions (I) and (III), add

1.5 c.c. of solution (II) and dilute to 20 c.c. Determine in both

samples the degree of rotation. If the polariscope is not very

sensitive, use instead of the first mixture one which contains 5 c.c.

of solution (I).

If c is the concentration of the malic acid, I the length of the

tube (usually 20 cm.), and an the angle of rotation read with

sodium light, then the specific rotation is [a]D = ~. The

C • t

experiment with malic acid gives for the value of [ao] about

—3°, with uranyl-malic acid, about —475°.