396 



Journal of Agricultural Research 



Vol. XV, No. 7 



Eighty gm. of air-dried spinach material were introduced into two 

 500 cc. round-bottom flasks (about equal amounts), and 200 cc. of 

 boiling hot ammonia-free water added to each of the flasks, which were 

 now kept on the water bath for 10 to 15 minutes. The digested spinach 

 was then sucked off through a Buchner funnel, provided with a linen 

 cloth filter (instead of a paper filter which filters very slowly). The cake 

 remaining on the Buchner funnel was transferred to the round-bottom 

 flasks, hot water added to original volume (about 150 cc. water to each 

 flask), kept on the steam bath, etc., the exi:raction having been effected 

 altogether four times. The combined extracts were distinctly acidified 

 with acetic acid, using a small excess of it, and boiled for a few minutes. 

 The extracts so treated were then filtered and washed on a Gooch crucible 

 provided with a paper-pulp filter which, as was shown by Jodidi and Kel- 

 logg, proved to be an efficient filter not only for the estimation of phos- 

 phoric acid (25), calcium and magnesium (26), and in general for quanti- 

 tative analysis (27), but also for the separation of solids from liquid {28) 

 in general chemical work, especially when a comparatively small precipi- 

 tate is contained in a large volume of liquid. On cooling, the liquid 

 was made up to 2,000 cc, of which two or three portions of 25 cc. each 

 were oxidized according to Kjeldahl's method to ascertain the amount 

 of nitrogen extracted. The data are summarized in Table VI. 



Table VI. — Nitrogen in water extract of healthy and diseased spinach 



A glance at Table VI shows that under the conditions outlined the 

 proportions of nitrogen extracted by water from the various spinach ma- 

 terials were fairly uniform, this being true of both the healthy and the 

 diseased plants. When we further compare No. i and 2 of Table VI 

 with No. I and 1 3 of Table IV, first section, we find that the total sum of 

 the water-soluble nitrogen and the protein nitrogen is from i to 2 per 

 cent above 100, this being undoubtedly due to the fact that the Stutzer 

 method ordinarily yields a somewhat too high percentage of protein 

 nitrogen. The discrepancy is, however, greater in the case of the diseased 



