RECENT ADVANCES IN SCIENCE 635 



(Berichte, 1 9 1 5 , 48, 1 5 1 7) have accordingly taken up this ques- 

 tion once more, making use of a series of reactions in which no 

 substitutions are called into play and which all take place at 

 low temperatures, thereby reducing the chances of a Walden 

 inversion to a minimum. Starting with the optically active 

 half amide of ethyl isopropyl malonic acid 



C 2 H 5V /CONH 2 

 C 3 H/ \COOH 



they have obtained b}' the action of nitrous acid the optically 

 inactive ethyl isopropyl malonic acid, thus demonstrating the 

 equivalence of the two carboxyl groups. Similarly, dextro- 

 rotatory allyl propyl cyanacetic acid 



C 3 H 5 . 7 CN 



c 3 h/ \:ooh 



on reduction has yielded the inactive dipropyl cyanacetic acid 

 which proves the equivalence of the two alkyl groups. It is 

 proposed next to prepare the optically active form of vinyl 

 ethyl cyanacetic acid 



CH 2 = CH V .CN 



C 2 H 5 / \C00H 



and to reduce a portion of it to the inactive diethyl cyanacetic 

 acid and also if possible to oxidise some of it to ethyl cyano- 

 malonic acid 



COOH v ,CN 



C 2 H 5 / x COOH 



If these latter reactions are successfully accomplished the 

 equivalence of all the four valencies will have been established. 



The intricate question of the assimilation of carbon dioxide 

 by the plant forms the subject of an interesting paper by 

 Willstatter and Stoll {Berichte, 191 5, 48, 1540). The authors' 

 method of experimenting was to pass a regular stream of air 

 containing a known amount of carbon dioxide through a small 

 illuminated glass vessel immersed in a constant temperature 

 water bath and containing from 5 to 20 grams of leaves. By 

 estimating the amount of carbon dioxide in the issuing gas 

 and the amount of chlorophyll in the leaves they determined 



