( 69) 



when we consider thai by inoculation of a nialate film into propio- 

 nate or acetate as abundant cultures are obtained as in the said 

 crude cultures in these media. Hut if it is tried to continue such cul- 

 tures by re-inoculating anew into propionate or acetate they also 

 soon lose their power of' growth. From this we see that the pre- 

 ceding culture conditions to which (he inoculation material has been 

 subjected, are by no means indifferent to the vitality of the following 

 generations, which are evidently very easily weakened and then 

 nearly quite lose the faculty of fixing nitrogen. The importance of 

 this fact cannot be denied and certainly deserves a nearer examination. 



Calciumcitrate, calciumtartrate and calciumsuccinate, with either 

 garden soil or canal water for infection, give but slowly a mode- 

 rately developed bacteria film but it grows during a very long time. 

 The film on the citrate is rich in spirilla and the Azotobacter form 

 found in it differs in many respects from the ordinary varieties. 

 In all these cases the quantity of bacteria grown during the first 

 2 or 3 weeks, is still too slight to necessitate a determination of the 

 nitrogen, and could by a rough comparison with former computations 

 be valued at some tenths of milligrams N , 2 per gram of the dissolved 

 lime salt. After a Jong time however, the fixation of nitrogen with 

 these salts is also considerable. 



With calciumglycolate in absence of nitrogen compounds no 

 growth of microbes could be observed at all. 



2. Quantity of the fixed nitrogen. • 



Neglecting for the moment the volatile acid, to which we shall 

 return below, the analysis of the cultures is performed as follows. 



The whole quantity of the liquid, in which are present the cal- 

 ciumcarbonate formed by oxidation from the malate or the other 

 organic salt, besides the as yet not decomposed malate, the 

 salt of the volatile acid, and the bacteria, is treated with a known 

 quantity of normal hydrochloric acid by which the carbonic acid is 

 expelled on heating; a then following titration with normal alkali 

 and phenolphtaleine as indicator, shows how much calciumcarbonate 

 is produced and consequently how much of the organic salt is oxidised. 



After addition of a little sulphuric acid the liquid is evaporated to 

 dryness and after K.jeldahl's method examined on nitrogen, while 

 in each of the materials used the rate of nitrogen is stated separately . 

 The calciummalate of Merck, Darmstadt, proved nearly free from 

 nitrogen. 



