NEA YORK 



hUi'.ANiCAl 

 uaRDEN 



TORREYA 



\'ol. 36 No\cml)(M- December, 1936 No. 6 



Deuterium and living organisms 



ROHICKISON PrATI 



The existence of more than one variety of water is of great 

 interest to physiologists, and during the three years that deuter- 

 ium oxide, or heavy water, has been available for research many 

 investigators have studied its influence on plants and animals. 



Soon after Urey and his associates {33, 34) isolated deuter- 

 ium, an isotope of hydrogen, methods were developed for the 

 concentration of D2O, or deuterium oxide, from water by means 

 of electrolysis. Nearly all samples of water, whether from the 

 ocean, fresh water lakes, or formed by the combustion of or- 

 ganic matter, contain about 1 part in 5000, or 0.02 per cent, 

 D2O by weight. To isolate the D2O from water, use is made of 

 the well known fact that when an electric current passes through 

 water, oxygen and hydrogen are liberated at the electrodes.^ 

 At first relatively more light than heavy hydrogen is liberated. 

 Consequently as the treatment proceeds the ratio of heavy to 

 light hydrogen in the residue increases and ultimately oxygen 

 and deuterium are liberated. The gases are then burned and 

 just as two atoms of hydrogen (mass= 1) may combine with one 

 atom of oxygen to form a molecule of H2O, so two atoms of 

 deuterium (mass = 2) combine with one of oxygen to form D2O. 

 The cost of the current consumed is the greatest item of expense 

 in this procedure, but improved methods and increased efh- 

 ciency have combined to reduce the cost of production from 

 about one dollar to approximately ten cents a drop. 



Influence of D^O on growth. — High concentrations of D2O 

 have been found in a number of cases to exert a depressing ac- 

 tion on the normal growth of plants and animals. Tobacco 

 seeds were found to sprout slowly in 50 per cent D2O and not 

 at all in 100 per cent D2O (14, 15). Seeds were not killed, how- 



1 Numbers in parentheses refer to literature citations. 

 '^ In practice a dilute sodium hydroxide solution is prepared with the water 

 to be concentrated. This facilitates electrolysis (4). 



133 



