3 2 Ö PLANT AND ORGANIC CHEMISTRY 
rays of polarized light, which are turned to the right or left, 
depending upon the isomer, the acids are known as the right 
and left lactic acids. In uniting they give an inactive form. 
In connection herewith, it may be well to mention the tar¬ 
taric acid experiments of Pasteur. On working with certain 
of the salts of that form of tartaric acid called racemic acid, 
he noticed that he could separate them into two crystalline 
forms, which in aqueous solution behaved differently towards 
polarized light. According to the direction that the solutions 
of the crystals turn the plane of polarized light, they are known 
as the salts of the right and left tartaric acids. The corre¬ 
sponding acids contain two symmetrical and two asymmetri¬ 
cal carbons. They may be represented in this manner: — 
Right Tartaric Acid. Left Tartaric Acid. 
COOH COOH 
H—C—OH OH—C—H 
I I 
OH—C—H H—C—OH 
I I 
COOH COOH 
The two active modifications may he brought together, and 
when united, give the inactive form, or racemic acid. 
COOH 
OH— 
H 
-H 
—OH 
COOH | 
H 
OH— 
COOH 
OH 
—H 
COOH 
The inactive acid may be separated into its active compo¬ 
nents by chemical means, or by the action of certain ferments. 
These ferments have the effect of destroying either the right 
or the left modification. 
There is another inactive form of the acid, known as the 
