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This experiment was carried out for the purpose of elucidating the depression effect of sulfurous acid on the sulfide minerals in a flotation. The floatability of sulfide minerals were measured with varing the concentration of sulfurous acid by using Hallimond tube, and the critical curves of each mineral were determined.And then, the depressant action of sulfurous acid was discussed through the calculation of the concentration of H2S03, HSO3-and SO3-in solution.The results obtained are as follows : (1) The depressing effect of sulfurous acid on the sulfide minerals decreases in the following order Pyrite, Sphalerite, Galena, Chalcopyrite. The activated sphalerite is hardly depressed.(2) The depressing effect of sulfurous acid and sodium sulfite on the sulfide minerals is almost the same.(3) From the result of calculation of the H2SO3, HSO3-, SO3- concentrations along the critioal curves, it is recognized that the SO3-concentration is nearly constant for Galena, Chalcopyrite and Pyrite.The results are almost the same as in the case of sodium sulfite and it is considered that the depressant action of both reagents is mainly based on SO3-concentration.

Lead smelter slags from two different sources have been leached using sulfurous acid/oxygen as the leachant so as to dissolve zinc and copper values but not the contained iron. The differences in the leaching behaviour are explained in terms of the different slag compositions. The mixed control shrinking core model adequately described the relationship between fractional extraction and time.

The free energy of formation of dimethyl sulfite in aqueous solution can be calculated as −91.45 ± 0.79 kcal/mol; this calculation required measurement of the solubility of dimethyl sulfite. From this value and the pKa of SO(OH)2, using previously reported methods, the free energy of formation of SO(OH)2 can be calculated to be −129.26 ± 0.89 kcal/mol. Comparison of this value with the value obtained from the free energy of formation of 'sulfurous acid' solutions, calculated from the free energy of formation of sulfite ion and the apparent pKa, values, permits evaluation of the free energy of covalent hydration of SO2 as 1.6 + 1.0 kcal/mol, in agreement with earlier qualitative spectroscopic observations. From the apparent pKa and the anticipated pKa values for the tautomers (SO(OH)2, pK1 = 2.3; HSO2(OH), pK1 = −2.6) it is possible to calculate the free energy change for tautomerization of SO(OH)2 to H—SO2(OH) as +4.5 ± 1.2 kcal/mol. All equilibrium constants required for Scheme 1, describing the species present in dilute aqueous solutions of SO2, have been calculated. In agreement with previous Raman studies the major tautomer of 'bisulfite ion' is calculated to be H—SO3−.

Conductometric measurements of the catalytic oxydation of dilute aqueous sulfurous acid were used in the comparison of various carbon catalysts, e.g. active charcoals and carbon blacks. The oxidation rate is proportional to (Po2) 1/2 and to the amount of adsorbed HSO3- ions. Basic surface oxides are responsible for the HSO3 -adsorption. The catalytic activity of a carbon is influenced also by other factors than the concentration of basic surface oxides. It is changed by heat treatment of the carbon as well as by chemical treatment of its surface. Treatment with ammonia at 600 °C increases its activity dramatically, absolutely inactive carbon blacks were rendered highly active.

Standard enthalpies of ionization of sulfurous acid and the standard enthalpies of solution of Na 2 SO 3 (s) and Na 2 S 2 O 5 (s) in water at 298.15 K were measured by solution-reaction calorimetry. All operations were carried out under N 2 with particular care to exclude O 2 from the reaction system. Steps in the corrections to the standard states are outlined in detail. The results (mean ± uncertainty interval) are: Δ ion H m ∘ (H 2 SO 3 , aq) = −(17.82±0.18) kJ·mol −1 ; Δ ion H m ∘ (HSO 3 − , aq) = −(3.67±0.06) kJ·mol −1 ; Δ sol H m ∘ (Na 2 SO 3 , s) = −(13.26±0.06) kJ·mol −1 ; and Δ sol H m ∘ (Na 2 S 2 O 5 , s) = (21.34±0.07) kJ·mol −1 for the process: Na 2 S 2 O 5 (s)+∞H 2 O(l) = 2NaHSO 3 (aq). For the equilibrium: 2HSO 3 − (aq) = H 2 O(l)+S 2 O 5 2− (aq), we selected K ∘ = 0.032 and Δ r H m ∘ = −4.2 kJ·mol −1 from the litrature.

Corrosion rate data are presented for low carbon steel in (1) a combination of sulfur dioxide, water vapor and air, and (2) aqueous solutions of sulfurous acid in the absence of air, at ordinary temperature. Information as to the nature of the corrosion products is presented and it is shown that this depends on the place in which the corrosion takes place to an important extent.

After staining for the Feulgen nucleal reaction with Schiff's reagent, slides were immediately submerged in running distilled or tap water and washed for 30 sec or longer. Rapid and complete removal of residual Schiff's reagent from the stained tissue will give preparations which show all details characterizing the nucleal reaction, and which are more durable in storage than those processed with the customary washing in a solution of SO2. Care must be taken to insure that all parts of the slides are thoroughly washed and that, on the surface of the sections, no spilled adhesive or other interfering coating retards the washing. Standardization of the procedure for quantitative DNA determination may be facilitated by this modification.

Two isomeric 10,10-dihydro-endosulfans are isolated, and their configurations are determined by means of infrared and nuclear magnetic resonance spectra. The isomerisation of the sulfurous ester ring of 10,10-dihydro-endosulfan yields a 67/33 ratio for the α/β isomers, while the endosulfan gives a 45/55 ratio. Both the 10,10-dihydro-endosulfans prove to be less easily hydrolised than endosulfan.