4IO 



Journal of Agricultural Research 



Vol. XIII. No. 8 



the weight of water absorbed must have been far below the quantity 

 which the P gluten could imbibe and still remain coherent. We are 

 forced to conclude, therefore, that not only does the weak gluten have a 

 lower rate of imbibition than the strong gluten, but that it also has a 

 much lower maximum hydration capacity; or, in other words, a gluten 

 from a "weak" flour changes from a gel to a sol at a much lower degree 

 of hydration than does gluten from a strong flour. 



In short, the difference between a strong and a weak gluten is that 

 between a nearly perfect colloidal gel with highly pronounced physico- 

 chemical properties, such as pertain to emulsoid gels, and that of a 

 colloidal gel in which these properties are much less marked. 



Fig. i6. — Graph showing the imbibition curves for C gluten in hydrochloric acid and in hydrochloric add 



plus certain salts. 



COMPARATIVE MEASUREMENTS OF THE HYDRATION CAPACITY OF 

 THE DIFFERENT GLUTENS IN VARIOUS CONCENTRATIONS OF 

 LACTIC, ACETIC, PHOSPHORIC, OXALIC, AND HYDROCHLORIC ACIDS 



It will be observed that the curves in figures 1,2, and 3 are very dif- 

 ferent in form from those of figures 4 and 5. Upson and Calvin {14) 

 observed similar differences between the curves for lactic and acetic 

 acids and that for hydrochloric acid. 



Both hydrochloric and oxalic acids are highly ionized when compared 

 with the other acids, ^ although phosphoric acid has a dissociation con- 



' Abbott and Bray {i.p.760) give the following ionization constants: Ortho-phosphoric acid (H2PO«~+ H+) 

 I.I X 10-2, (HP04~+K+) I.9SX 10-', acetic acid 1,8 x io-6,and boric acid 1.7 x lo"". They give the constant 

 for hydrochloric acid as 6 x io~'. This is possibly a typographical error, for Noyes {iz, p. 860) gives the 

 ionization constant for hydrochloric acid as i, with those for acetic and phosphoric acids of the same value 

 as given by Abbott and Bray. Landolt-Biimstein (11, p. 1147) give constants for oxalic and lactic acids as 

 3.8 X io~* and 1.38 X io~*, respectively. 



