RESULTS or EXPERIMENTS. 



27 



RESULTS WITH SODIUM CARBONATE. 



The following table gives the results with pure solutions of sodium 

 carbonate : 



Name of wheat variety. 



Zimmerman 



Kharkof 



Padui - 



Kubanka 



Turkey _ _ - 



Maraouani - _- 



Budapest 



Preston 



Chul -_ 



Average for all varieties 



Maximiim limit of 

 endurance. 



Partsper!Ff^^^;°"f 



solution. 



m 



78 

 52 

 39 

 78 

 41 

 26 

 65 

 65 



normal 

 solution. 



0.(1125 

 .015 

 .01 

 .0075 

 .015 

 .008 

 . (H k') 

 . 0125 

 .0125 



.0109 



The results shown by the above table are not materially different 

 from those with magnesium chlorid. Sodium carbonate in pure 

 solutions is slightly less harmful, as shown by the comparison of the 

 average of all the varieties, being in the case of magnesium chlorid 

 O.OOO:^ and for sodium carbonate 0.0109 of a normal solution. The 

 extremes in both cases are the same, though there are two varieties 

 with a resistance of 0.015 for sodium carbonate as against one for 

 maanesium chlorid. Five varieties in the case of sodium carbonate 

 have a resistance above the average as against four in the case of 

 magnesium chlorid. One variety alone, Budapest, has a resistance 

 of only 0.00.5 as against two for magnesium chlorid. 



Of the three salts so far described, sodium carbonate is in the soil 

 generally the most harmful, (1) because in excessive quantity it is 

 more widely distributed, and (2) because it is less easily neutralized 

 by other salts with which it is usually associated. 



The opinions of experimenters differ considerably as to the rela- 

 tive toxic effect of this salt. Kearney and Cameron showed that, in 

 the case of Lvphius alhus at least, sodium carbonate is but little 

 more injurious than sodium sulphate, the toxic limit in each case 

 being 0.005 and 0.0075 of a normal solution, respectively. It will be 

 seen that the limit for the lui)ine obtained by them with sodium car- 

 bonate is the same as the resistance for Budapest wheat, but only 

 one-third of that for the Turkey and Kharkof varieties. The limit 

 of concentration for the lupine, as shown by their report, is about 

 equivalent to one-half of the average for the several wheat varieties, 

 ill the same salt solution. Kearney found Zea mayfi to survive in 

 the same salt at a concentration three times as great as that repre- 



