ROTATION OF TARTARIC ACID

and /'/the density of the solution. The specific rotation of dis-
solved substances varies with the concentration and with the
temperature.

Heat some tartaric acid in an air-bath to 110°, until it is quite
dry. Weitfh accurately about 20 grams of the dry acid and
dissolve in water ; then make up the solution to exactly 100 c.c.
Determine the rotation of the solution in a 200 mm. tube, and
note the temperature at which the observation is made.

Take 50 c.c. of the solution and dilute it to 100 c.c. Deter-
mine the rotation of this solution tif ///<• same fcmpcmhtrc as
that at which the first rotation was observed.

Dilute' 50 c.c. of the second solution to 100 c.c., and a^ain
determine the rotation at the same temperature.

The same process can be repeated once or twice more. Cal-
culate the specific rotation of the tartaric. acid, usinjj the Iirst
formula. Plot the results on squared paper, making the ordi-
nates specific rotation and the abscissae concentration.

Example :—

Temp.

IO

10"
10"

Concentration.

40
2O
IO

Length of tube.

Auyjc of Rotation.
Spec. Rut. '^'"

6"
•!- 7*5"

3° 59'
•I <r<K>"

2" II'
•i 10-91"

(Krcckc, />V.v.•//«.'//,' ,SWmv//<v///V, p. :•-.•;•;.)

The following table shows the influences of temperalinv on
the specific rotation of an aqueous sululion containing 20 grains
of tartaric acid in roo c.c.

o

10"
20°

40°
60°

So0

100°

K,,,:,,i,,
Sprrilir 1
„,„!„„.

3
2,X'
•! S
oO"

3
5<i'
-1 o
()(>''

4"
?<v*'
1 II
57"

5"
2S'
-1 rj
00"

<r
2S'
-1 lO
10"

7"
2l'
•( iS
3^

8°
*<>'
1 21
50'

(Thoniscn,,/. prakt. Ck, (a) r-', an.)