Technique for measuring metallic salt effects upon the indigenous heterotrophic microflora of a natural water

The effects of several concentrations of the metallic salts Ag₂SO₄, NaAsO₃, BaCl₂2H₂O, CdCl₂2.5 H₂O, CrCl₂6H₂O, CuCl₂, HgCl₂, NaCl, NiCl₂6H₂O, PbCl₂ and ZnCl₂ upon the indigenous heterotrophic microflora of a natural water were studied. Effects of these salts upon the heterotrophic activity of the microbes were assayed using the heterotrophic technique whereas lethal effects upon the heterotrophic bacteria were determined using nutrient agar plate counts. The heterotrophic activity method is based upon the uptake and mineralization of a radioactively labeled metabolite (in these experiments ¹⁴C-glucose) by the indigenous aquatic microbes and data analysis is by Michaelis—Menten enzyme kinetics equations. Concentrations of metallic salts which resulted in bacterial death also caused erratic uptake and mineralization rates of ¹⁴C-glucose whereas sub-lethal concentrations, as determined by nutrient agar plate counts, caused a non-competitive inhibition of maximum heterotrophic activity and markedly increased the turnover time of the glucose substrate.     

Gravity driven counterflow through an open door in a sealed room

Flow measurements using tracer gas techniques were made on the exterior doorway of a test house for indoor-outdoor temperature differences of 0.5–45 K. The time for door opening and closing was constant at 3.75 s, and fully open hold time varied from 0.5 s to 120 s. Predictions of a variable density steady flow model were in good agreement with the measurements when adjustments were made for the time-varying size of the opening and for the effect of cross-stream mixing between the incoming and outgoing air streams. The flow rate is shown to be governed by an effective density very close to the average of inflow and outflow densities, and the control condition at the doorway is fixed by the jet-like behavior of the inflow stream. Dependence of cross-stream mixing on interfacial stability caused the orifice and coefficient to increase from 0.4 to 0.6 as temperature difference increased. This varying orifice coefficient is well represented by the combination of a discharge coefficient for streamline contraction combined with a mixing coefficient which accounts for mixing between the inflow and outflow.     

Interaction of bacteriophage R17 and reovirus type III with the clay mineral allophane

A study has been made of the adsorption of bacteriophage R17 and reovirus type 3 by the amorphous aluminosilicate clay mineral allophane. In agreement with previous studies of virus adsorption to other minerals such as montmorillonite and aluminium hydroxide, the principal factors influencing adsorption were found to be mixing time, pH and the concentrations and isoelectric points of both the virus and the absorbent. However, allophane was found to be a much better adsorbent for reovirus and R17 over the pH range 5–7, the natural pH range of many fresh waters.By using highly purified radioactive reovirus it was possible to follow both the distribution of radioactive virus in a clay suspension and the specific infectivity of the virus. This study revealed that when adsorbed virus was eluted by neutral phosphate solutions it retained its physical integrity but was of a lower specific infectivity.     

The manual determination of ammonia in fresh waters using an ammonia-sensitive membrane-electrode

The use of a commercially-available ammonia-sensitive membrane-electrode for the manual determination of ammonia in discrete samples of fresh water has been investigated and the analytical procedure is described. The electrode is simple and convenient to use, and a sample can be analyzed in a few minutes. For normal routine analysis, the lower limit of determination is approximately 0·1 mg N 1⁻¹ though smaller concentrations can be measured. The relative standard deviation of analytical results varied from approximately 10 to 3 per cent as ammonia concentration increased from 0·1 to 4 mg N 1⁻¹. Results for samples of river water agreed well with those obtained by absorptiometric methods of analysis; the electrode responds to amines but otherwise appears to be essentially specific for ammonia. Use of the electrode will be advantageous in a number of applications, and it also has good potential for the on-line analysis of fresh waters.     

SUBSTITUTION OF TOPAZ,DOMESTIC KYANITE,AND SYNTHETIC MULLITE-CORUNDUM FOR INDIA KYANITE,I–III*

This report on the utilization of domestic materials as replacements for India kyanite has been divided into four parts, namely, (I) kyanite and other high-grade refractories, (II) effect of heat on kyanite and topaz, and (III) load resistance of refractories at elevated temperatures; (IV) will be published later.