106 THE ROLE OF NITROGEN IN PLANT-METABOLISM, iii., 



and water added so that, maiutaiuing the same volume cf 

 liquid throughout, the strength of spirit ranged from 10 to 

 80%. These tubes were allowed to stand over night to 

 deposit, then spun in the centrifuge. After decantation of 

 the superfluid, the deposits were transferred to small, accur- 

 ately weighed centrifuge-tubes, washed once with alcohol of 

 the same strength, followed by two washings with absolute 

 alcohol, and finally with dry ether. The tubes were next 

 dried carefully at SC" C. in the oven, finally at 110* to con- 

 stant weight, and weighed under exact conditions. The 

 contents of each tube were then shaken out into a weighed 

 platinum crucible, and the tubes reweighed. The dry white 

 powder was incinerated, and the weight of the ash deter- 

 mined. The weight of ash-free protein was thus obtained. 



{h In a precisely similar series of duplicates precipitated 

 under the same conditions, as nearly as possible, the moist 

 deposits, after washing with alcohol of the same strength, 

 were each transferred to a Kjeldahl flask, and the nitrogen 

 estimated. 



The details of these experiments are tabulated below: — 



Table vi. 



These results are plotted in the accompanying curves, of 

 which the ordinates represent — in A, the weights of nitrogen 

 in milligrams; and in B, the weights of precipitate in centi- 

 grams. Abscissae represent the percentages of alcohol present. 



