326 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 



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. 



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 



