Sodium arabinate

Such preparations can be analysed for their content of metal, which will enable one to calculate their equivalent weights. Sodium arabinate gave in this way the mean value of 1202, a figure which after subtraction of 22 (i. e. — Na + H) is in good agreement with the equivalent weight of arabinic acid, viz.y 1177, found by Thomas and Mxtrray from titration curves of the latter substance in solution. 

As was already stated in Ch. VII, p. 223, hexol nitrate, a complex cobalt salt with hexavalent cation, flocculates or coacervates most biocolloids of acidic nature, thus also gum arabic and sodium arabinate sols. Here the remarkable situation is encountered, that the hexol nitrate concentration needed just to start coacervation is nearly proportional to the arabinate concentration, this fact already indicating that the expression hexol nitrate concentration is here of a doubtful value the hexol cations cannot be freely present in solution but must combine with the arabinate. 

If now dilute sodium arabinate sols of different concentrations are investigated, it appears that the hexol nitrate concentration required to reach exactly the reversal of charge point, is a strictly linear function of the colloid concentration, as shown in Fig. 2. The straight line obtained extrapolated to zero colloid concentration intersects the ordinate axis at very small positive value (4.10- N) thus indicating that we obtain two different kinds of information regarding the reversal of charge phenomenon. 

When 2,3-O-isopropylidene-D-gulono-1,4-lactone (52) was treated with sodium periodate, 3,4-O-isopropylidene-L-lyxurono-l,4-lactone (84) was formed26 this was converted in several steps into D-arabin-ose. Benzyl 2,4,5,6-tetra-O -benzyl-L-gulonate was oxidized to benzyl... 

Fio, 1.—Curves for Light-absorption in the Dische Test (o) 2-Desoxy-D-ribose (61) D-Arabinal (i2) L-Arabinal (c) Furfuryl alcohol (d) w-Methoxylevulinaldehyde Dimethyl Acetal (e) Sodium Thymonucleate (/) Methyl 2-desoxy-/3-n-ribopyrano-side (g) Methyl 3,4-Dimethyl-2-desoxy-/3-L-ribopyranoside. 

The protected 2-formyl-L-arabinal reacted with thiourea and cyanamide in the presence of sodium hydride to afford, via ring transformations, the 5- [ lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl]- 1,2-dihydropyrimidines. Similarly, treatment with 3-amino-2H-1,2,4-triazole yielded 6-[lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl][l,2,4]-triazolo[l,5-a]pyrimidine [151]. Reaction of 27 with 2-aminoimidazole and 2-aminobenzimidazole gave 96 and its bezo-analogues [64]. 

L-Ascorbic acid, an enediol, has been oxidized by sodium hypoiodite and by potassium permanganate to L-threonic acid (9). Such oxidation of double bonds does not occur in the enols alone, for D-arabinal is oxidized by H2O2 and OSO4 in er butanol to D-erythronic acid in addition to D-arabinose (10). Periodic acid and lead tetraacetate are useful for the cleavage of hexitols and glycosides to glyceraldehyde and glycolaldehyde (see Chapter... 

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