EXPERIMENTS IN CHEMISTRY 27 



acterized the tartrates of many substances, how- 

 ever different the form of their crystals might 

 otherwise be. Pasteur then turned his attention to 

 the paratartrates or racemates. These substances 

 had been proven by chemical analysis to be of the 

 same chemical composition as the tartrates. They 

 had the same specific gravity and many other 

 properties in common, and were held also to have 



Fig. 2. Right-handed and Left-handed Crystals of 



Tartaric Acid 



the same crystalline form, differing only in their 

 action on polarized light. By a careful study of 

 the crystals of the paratartrates Pasteur observed 

 that some of them were right-handed and others 

 left-handed. He then carefully separated out these 

 two types of crystals, dissolved them, and examined 

 the solutions with a polariscope. To his great joy 

 he found that the solution made from the right- 

 handed crystals rotated the plane of polarization 

 to the right, and the solution of the left-handed 



