14 PASTEUR AND AFTER PASTEUR 



make up the complete plan of tartaric acid. He 

 was in quest of a left-handed tartaric acid, which 

 Science had never seen, nor dreamed of seeing. He 

 could only guess, that it might somehow be locked 

 up in racemic acid. 



At last, he found it. He prepared a double salt 

 of racemic acid, a sodium ammonium racemate, and 

 let it crystallise out : and these crystals were of 

 two forms, one having the facet of the commercial 

 acid, the other having the facet proper to the 

 unknown acid. Then he separated the two forms, 

 crystal by crystal; then, prepared two solutions, 

 one of each form : then, tested the solutions with a 

 polariscope : and there was the discovery. The 

 one form rotated the plane of polarisation to the 

 right : and the other, the form hitherto unknown 

 to the world, turned the plane, through an equal 

 extent, to the left. He had found the secret of 

 racemic acid : it was itself a combination of two 

 opposed forms : it held in itself both a right-handed 

 and a left-handed acid. He ran out of the labora- 

 tory, fell on one of the demonstrators, and 

 embraced him " I've just made a great discovery; 

 I've separated the sodium ammonium paratartrate 

 into two salts of inverse disymmetry and inverse 

 action on the plane of polarised light. The right- 

 handed salt is absolutely identical with the right- 

 handed tartrate. I'm so happy that I'm trembling 



