Reciprocal hexol number

RECIPROCAL HEXOL NUMBER AND EQUIVALENT WEIGHT CHARACTERISTIC CHARGE ELEMENTS... 

From the data represented in Fig. 2 the reciprocal hexol number of Na-arabinate was calculated to be 1068. Comparing this with the analytically found equivalent weight (see above), for which 1202 was obtained, it appears that both values are of the same order, but are not equal, the reciprocal hexol number being smaller than the equivalent weight. 

Table 1 shows that in the colloids investigated the equivalent weight increases twelvefold and that the reciprocal hexol number also increases to the same order. But as with Na-arabinate the latter is always smaller than the former. Thus apart from a systematic difference — which is... 

From the slope of the straight line one calculates that the reciprocal hexol number (number of grams which binds one equivalent of hexol ions at the reversal of charge point) amounts to 294. The true reversal of charge concentration (segment of the ordinate axis cut off by the straight line) amounts to only 0.6.10- N. 

Substance Reciprocal hexol number Equivalent weight Reciprocal hexol number Equivalent weight... 

The figure shows the general effect in choosing a lower valent cation, which consists in a nearly parallel displacement of the straight line towards higher con-centrations. " The nearly equal slope of both lines means that the reciprocal La number will indeed be practically the same as the reciprocal hexol number. The main effect consists thus in an enormous increase of the real reversal of charge concentration, the latter being 7 X 10 N for hexol nitrate and 3.6.10 for La(NOg)3. 

Thus the accuracy of a calculated reciprocal La number must be necessarily much lower than of a reciprocal hexol number. 

Still the systematic difference between the numerical values of reciprocal hexol numbers and equivalent weights calls for an explanation. This discrepancy is not easily explained from considerations in homogeneous media. 

We come now to the difficulty proper, mentioned already above viz., that the reciprocal hexol number is somewhat smaller than the equivalent weight. 

If we assume that the coacervate which contains only hexol arabinate has no double layer at the surface of its drops as indicated in B, then reciprocal hexol number and equivalent weight should be exactly equal. 

This is shown in the following Table 2, in which fourteen colloids are listed in the order of decreasing reciprocal hexol number. The table contains information on the flocculability with six different salts, viz., hexol nitrate (6—1) rhodochromium chloride (5—1) platinium triethylenediamine tetranitrate (4—1) luteocobalt chloride (3—1) CaCl2(2—1) and NaCl(l—1). 

Inspecting the above table, we see that the first three colloids with very high reciprocal hexol numbers do not flocculate with either of the six salts. The next colloids with reciprocal hexol numbers ranging from 5 000—1 000, do flocculate or coacervate with 6—1, 5—1 and 4—1. 

The colloids with very low reciprocal hexol numbers show flocculation or coacervation with 6—1, 5—1, 4—1, 3—1 and in some instance even with 2—1. Thus it seems that the equivalent weight (which multiplied by approximately 0.85 is the reciprocal hexol number) is an important factor in determining flocculability with salts of the types considered here. 

On closer inspection of Table 2 on page 270, we see that the correlation between reciprocal hexol number and flocculability is not a rigorous one, so, for instance, Na agar though of lower reciprocal hexol number than the preceding Soya bean phosphatide, shows only opalescence with 6—1. 5—1 and 4—1. 

As abscissa values are taken not the reciprocal hexol numbers (R.H.N.) themselves, but the thousand-fold values of their... 

Fig. 5. Relation between tendency to flocculation or coacervation and reciprocal hexol number (upper) or equivalent weight of the colloid anion (lower). (See text).

In tricomplex systems (Ch. X 6 p.415) however this no longer holds. Here the amphoions of the phosphatide preparation form the reacting component of the mixture, and the phosphatidic anions present are only a nuisance. Therefore the said tricomplex systems are the more typical the higher the reciprocal hexol number, that is the fewer phosphatidic anions are present. 

In accordance with it preliminary experiments on the influence of pH on the reciprocal hexol number of arabinates showed that the value of the latter is practically constant in the pH range 6.2—4.5 and that only at lower pH values a change takes place in the expected direction. 

The general equation may for instance approximate to C = Cft which at moderate sol concentrations is the case for hexol nitrate, Q here being very small. Therefore hexol nitrate is a salt which is well fitted to give information on the charge density of colloids as was discussed in details in 1. In that section Q was the only quantity which really interested us, leading to the calculation of reciprocal hexol numbers. The very small and not exactly measurable Ct values had only the importance of a correction factor used in the calculation of Cf from the experimentally found C values at a few sol concentrations. 

In Fig. 20 a number of ion spectra for different phosphatide preparations are given. They have been arranged in the order of decreasing reciprocal hexol number, the uppermost showing the highest (76 000), the lowest one showing the lowest reciprocal hexol number (782). 

Fig. 20 shows, that the characteristic sequence of cations is in all the same (or practically the same), only the spread is greatest with low charge density", this becoming less with increasing charge density" (i.e., with decreasing reciprocal hexol number). 

We may add that the reversal of charge with H ions (not marked in the figure) also shows the same behaviour, the LE.P, shifting from higher to lower pH values with decreasing reciprocal hexol numbers. 

Phosphatides are extremely difficult to obtain in a pure state. The phosphatide preparations used must be considered as mixtures of pure phosphatides (ampholytes) and phosphatidic acid, the latter giving the phosphatide preparation the character of a colloid of acidic nature . The purer the preparation the higher the reciprocal hexol-number, the higher also the LE.P. and as shown in the figure the lower the reversal of charge concentrations for polyvalent cations (e.g., Ca). 

Fig. 20. Reversal of charge spectra for a number of phosphatide preparations with different reciprocal hexol numbers (RHN).

The number of cations in this figure is reduced to the minimum which suffices to bring out the phosphate colloid character of the phosphatides. This figure shows that the higher the reciprocal hexol number (i.e. the closer the phosphatide preparation approximates to pure phosphatide) the lower the reversal of charge concentrations come out (for the rest this displacement does not make its appearance with Na and K) (see further text). 

We see further, that the antagonism becomes more and more pronounced as the value of Q increases. Combining these facts with the role of the reciprocal hexol number (or apparent equivalent weight) in determining the spread of cations in the... 

Alongside the colloids are given the reciprocal hexol numbers (p. 270, as a measure of the colloid equivalent weight) determined on the colloid preparations used. 

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