Rate Of pH Change Research Articles

Sephadex‐Gelfiltration von Huminsäuren und deren Gehalt an Aminosäuren

Gel filtration on Sephadex of humic acids and their content of amino acids Brown humic substances from the Ah of an iron‐humus podzol were separated on Sephadex G 25 into three fractions. The first fraction (Ve/Vo = 1.0–1.5) has the lowest value of Q 4/6 (5.0–8.0), the second the highest Q 4/6 (10.0–12.0) and the third a middle one (8.0–10.5). The adsorption effect may take place during separation. The asymmetric form of the integral elution curves of the first fraction indicated that the humic substances are a set of particles with different size. The separation is influenced by diffusion into the pores of gel matrix. In the first fraction were determined 16, in the second 13 and in the third 10 amino acids. The titration curves of the first fraction (after separation on G 25) indicated that the rate of pH change with alkali added becomes its maximum at pH 6.5–7.5 at different ionic strengths. Dialysed humic acids (H+ form) were fractionated on G 75. The alkali consumption up to pH 7.5 in the eluate shows that small amounts of mineral acids increase the conductivity of the solution. Their Ve is lower than that of the second fraction of humic acids. Therefore it is impossible to determine the alkali consumption by the second fraction and by the humic acids as a whole without their total desalting.

RATE OF CHANGE OF pH IN SOME ACID SOILS DUE TO LIMING

Lime at the rate of 0, 3000, 6000, 12,000 and 24,000 pp2m was applied to four acid soils and allowed to incubate for a period of 140 days. The rate and extent of change in pH was followed.In all four soils the rate of reaction was very rapid and most of the increase in pH was obtained within 3 days after application. At all rates of liming in the four soils there was a general decrease in pH following the peak obtained within the first 30 days.It was also found that the rate of change in pH of a soil that had been limed was greatly influenced by the moisture content. The change in pH was much more rapid and extensive at 25 per cent moisture than at 10 per cent.

The Relative Responsiveness of Certain Properties of Cotton Fiber to Microbial Action

In continuation of an inquiry into the effect of microbial action and weathering on cotton fiber, experiments have been carried out to determine the relative responsiveness of certain fiber properties to the growth of fungi. Raw cotton fiber and unbleached cotton fabric were inocu lated and incubated for varying periods up to 28 days in a water-vapor-saturated atmosphere with each of three common fungi under pure-culture conditions, and various properties of the fiber and fabric were measured subsequently. In general, the aqueous-extract pH and the reducing- substance content of the incubated samples changed quickly and substantially, the former in creasing and the latter decreasing. Degree of swelling in 18% NaOH and Congo red values changed little during the first few days of incubation, but later increased progressively. Strength, as measured on fiber by the use of a Pressley breaker equipped with 1-mm.-gap jaws or on fabric by the 3-in. ravelled-strip method on a Scott tester, showed little or no decrease. Length, determined by the Suter-Webb sorter method, decreased moderately with one of the fungi, but little if at all with the other two. Wax content decreased, but only moderately. Cladosporium-incubated fiber became measurably and visibly darker. Absorption of the direct dye Chlorantine Fast Green by fiber incubated with Cladosporium and mercerized before dyeing increased markedly with increasing periods of incubation. Incubation at 95% R.H. greatly slowed down the rate of change in pH and reducing-sub stance content as compared with results obtained in a saturated atmosphere and prevented change in the alkali-swelling response.