Constituents of Biocolloids Affecting Hydration and Growth. 



33 



TABLE 14. 



Water. 



p. ct. 

 1,025 



Potassium nitrate, 0.0 M 950 



Potassium nitrate, citric acid, 0.01 N 675 



Citric acid, 0.01 N 650 



Potassium nitrate, potassium hydroxid, 0.01 M 775 



Potassium hydroxid, 0.01 M 575 



The comparative test of the result of the inclusion of aspartic acid 

 and of its amine, asparagine, in the biocolloid is important, because the 

 amine is a noticeable constituent of plant cells, in which it is frequently 

 abundant. The acid appears to be only sparingly soluble and in a 

 plate of agar 90 parts and 10 of this acid aggregates as whitish lumps in 

 the plate or as an efflorescence on the surface. Much of the last form- 

 ation comes off, so that the proportions given above do not hold for the 

 dried material. The asparagine forms clear plates with the agar. 

 The swellings were as follows : 



TABLE 15. 



The asparagine mixture shows swellings in water, acids, and alkali 

 not widely different in proportion from those in which proteids of the 

 bean are used. The aspartic acid, in accordance with expectation, 

 shows an amplitude of swelling characteristic of organic acids in the 

 solution in both acid and distilled water as reagents. Neutralization 

 by hydroxid, and the renewal of this reagent, was followed by greater 

 sw^llings. 



The introduction of a fat into a biocolloid was attempted with a 

 preparation of lecithin (Merck) from eggs. An amount which would 

 give a proportion of about 0.5 per cent was smeared as a coating on a 

 glass stirring-rod. After half the contents of a flask containing a 

 mixture of agar 90 parts and milk albumin 9.5 parts had been poured 

 on a glass plate for drying, the remainder was stirred until all of the 

 lecithin had dissolved from the rod. It was then poured on a glass 

 slab to cool. Separate particles could not be distinguished with a 

 hand lens, but the mixture had a brownish tinge. When the film had 

 dried to a thickness of 0.2 mm. it was tested under auxographs at 16 

 to 18 C. and the swelling measurements given in table 16 obtained. 



No distinct effect of the fatty substance can be detected in these 

 reactions, nor were any departures discernible in another preparation 

 containing 90 parts of agar, 9 parts of bean protein, and 1 of lecithin. 

 The bean protein is a water extract of Phaseolus vulgaris containing 

 the albumins and also the other proteins soluble in the salts present. 



