482 



STATE BOARD OF AGRICULTURE. 



tohactcr species has been made by Mr. A, Itauo. The general ontline 

 of experiments correspondino; to the experiments X, XI, XT I. The 

 nutrient solution, a solution of 2%' dextrose and 0.02% Koin*U4 iu 

 tap Avater, was used as such and mixed with medium sand in the pro- 

 portions 20 : 200 and 50 : 100. The sterilized media were inoculated 

 with a pure culture of a freshly isolated AzotoTiactcr species and 

 the total nilrogen was determined after 7 weeks. 



TABLE XV. 

 Nitrogen fixation of Azotobacter in Sand Cultures, {mg N per 100 cc. solution). 



The results agree entirely with all those of the ]»r('vi(>ns expeiiments. 

 There is the same great increase of bacterial development of about 1000% 

 in the well ventilated sand over the plain solution, and the water-logged 

 sand is again a little superior to the solution without sand. The 

 amount of sugar used u]) has not been determined. 



Vinegar Bacteria in Sand and Solution. — As a further representative 

 of a strictly aerobic organism, the vinegar fermentation was used. 



The experiment was carried out as follows: The nutrient solution 

 was cider -f 8% alcohol, which was pasteurized for 2 hours at 80° and 

 was then inoculated with a 3'Oung pure culture of a vinegar bacterium 

 which is used as a vinegar starter. This inoculated cider was dis- 

 tributed with sterile i)ipettes into flasks containing each 100 g. of sterile 

 sand (medium quartz sand). The various mixtures, and the amounts 

 of acid formed by them at different times, are given in Table XVI. The 

 table shows only the acid actually produced, i. e. after subtracting the 

 acidity of the cider, in grams per 100 cc. of solution. The data are 

 averages from duplicate determinations. 



TABLE XVL 

 Acetic Acid formed from Alcohol in Sand and Solution. 



Culture. 



."> cc. -f 100 g Sand 

 10 cc. 4- 100 g Sand 

 15 cc. + 100 g .Sand 

 20 cc. -f 100 g Sand 

 25 CO. + 100 g Sand 

 .SO cc. -f 100 g Sand 

 50 cc. 4- 100 g Sand 

 75 cc. + 100 g Sand 

 100 cc. + 100 g Sand 



4 days. 



10 days. 



17 days. I 24 days. 



i 



0.12% 

 O.-SS^ 

 0.75% 

 3.33% 

 3.80% 

 4.90% 

 4.73% 

 0.23% 

 0.05% 



The experiment does not show the ('in|ili;isi/,iMl jioint very well because 

 the vinegar bacteria destroyed again the acid which they originally 

 fonned. This destruction is a complete oxidation and like all oxida- 

 tions takes place fastest in the driest sand. After 10 days, when the 

 sand with r»% moisture shows linrdly any acid, the sand with 20% 



