Abstract: The invention is concerned with an improved process for preparing paraffin-sulfonic acids containing from 10 to 20 carbon atoms, as well as their salts. The process comprises the initial reaction of sulfo-oxidation of the concerned mixture of n-paraffins, the removal of unreacted n-paraffins from the reaction mixture, the removal of the excess of SO.sub.2 from said mixture, and the removal from the reaction mixture of the therein formed sulfuric acid, with the simultaneous recovery of the end product.After the removal of SO.sub.2, to the reaction mixture hydrogen peroxide is added and the so obtained solution is submitted to one treatment selected from among the following treatments:(a) addition of an alcohol with a number of carbon atoms comprised within the range of from 4 to 8;(b) heating up to a temperature comprised within the range of from 50.degree. to 150.degree. C. and vacuum distillation under a residual pressure comprised within the range of from 5 to 500 mm.sub.

Abstract: The concentration of sodium metal in a flow of mercury-sodium amalgam is measured by flowing an aqueous solution of sodium chloride through a conduit of electrically insulating material terminating with a porous septum or a capillary immersed in the flow of mercury-sodium amalgam, at a rate of at least 4 ml per hour and per cm.sup.2 of surface area of contact between the surface of the porous septum or the section of the capillary opening and the amalgam, and monitoring the electromotive force generated between said amalgam and a calomel or silver-silver chloride reference electrode located within said conduit and in contact with said solution.

Abstract: The purity grade of sodium tripolyphosphate obtained by neutralization with sodium hydroxide of aqueous phosphoric acid obtained by the wet method, removal of the precipitate formed, evaporation to dryness of the resulting solution and calcination of the evaporation residue, is improved by carrying out the neutralization at a temperature not exceeding 85.degree. C., maturing the neutralization product at 70.degree.-85.degree. C. for at least one hour before separating the precipitate, concentrating the sodium phosphate solution, if necessary, to a sodium phosphate content of at least 40 wt.%, and heat treating the solution at 100.degree.-200.degree. C. and at boiling point or under to precipitate the magnesium compounds, prior to the evaporation step.