166 MacDOUGAL and SPOEHR— COMPONENTS AND 



inclusion in the carbohydrate, agar, increase its hydration in water, 

 and this holds true for such substances as asparagin, glycocoll, etc., 

 which cause a hydration much in excess of that taking place in water 

 when applied in aqueous solution. 



As a further contribution to this matter the hydroxides of cal- 

 cium, sodium and potassium were incorporated in biocoUoids in 

 proportions in which no lessening effect would be exerted by solu- 

 tions which would bring the same amount of the bases into action on 

 the colloids. The results of this series of tests are given in Table 

 XIII. 



The hydration values of the mixtures of agar 2 parts and gelatine 

 3 parts in water are not materially different from those of some col- 

 loidal mixture free from the bases. The presence of the bases in- 

 creases hydration in acid and in potassium hydroxide, but lessens it 

 in glycocoll, as may be seen by comparison with Table I. When the 

 proportion of agar is increased and that of gelatine decreased as in 

 a mixture of 3 parts agar and 2 of gelatine, the swelling in water is 

 lessened notably, and decreases occur in all solutions, a fact which 

 may be ascribed directly to the action of the carbohydrate compon- 

 ent. The bases included in these biocoUoids were present in pro- 

 portions one fourth of that in which excess sweUing was caused in 

 solutions of calcium and sodium, and one five hundredth in the case 

 of potassium, although the total amount of bases would be little 

 short of that present in any one of the solutions. 



It is suggested that the reversal of the effect of included bases on 

 the swelling of biocoUoids must be at a greater attenuation than 

 when in solution. Such restricting effect rises with the proportion 

 of carbohydrate present. 



It is evident that the inclusion of a substance or ion in a colloidal 

 structure results in hydration relations of a different character from 

 those which appear when the substance in question is presented in 

 the hydrating solution. In the latter case it seems theoretically pos- 

 sible that differentiations of external layers of the hydrating masses 

 may take place which might result in swellings due in the last analy- 

 sis to something like osmosis.* 



* MacDougal, D. T., " Hydration and Growth," Publ. No. 297 Carnegie 

 Inst, of Wash., 1920, see pp. 32, 33, 44, 46, 47, 48, 50, 58, 59, 70, 72, 75. 



