352 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC, Comparison of the Relative Efficiency of Laboratory Reflux Condensers. M. V. Dover and J. W. Marden. ( J . Ind. and Eng. Chem., 1916, 8, 834-836.)- The author has examined a number of condensers, among them being the Liebig, spiral, Allihn, Hopkins, Davies and Friedrichs. H. F. E. H. Surface Tension Measurements of Solutions of Soap and Soap-Alkali Mixtures.H. G. Elledge and J. J. Isherwood. ( J . Ind. and Eng. Chem., 1916, 8, 793-794.)-A comparative study has been made of a mixture of soap and various alkalis and alkaline mixtures marketed under trade names, to determine their relative detergent values. H. Jackson (Cantor Lectures, 1907) has shown that the values of the alkaline salts of weak acids-sodium carbonate, trisodium phosphate and borax- are equal when chemically equivalent weights are considered, and that sodium bicarbonate is practically valueless: a fact confirmed by the present authors.The apparatus employed was that described by H. W. Hillyer ( J . Amer. Chem. Xoc., 1903, 25, 511, 524, 1256), and consists of a 5 C.C. capacity dropping pipette, with capillary stem terminating with a perfectly plain surface 10 mm.in diameter, upon which the drops form in a bath of kerosene. A 0.4 per cent. solution of soap was investi- gated in conjunction with a 0.5 per cent. sodium carbonate or other alkalis in equiv- alent proportions, the drop number being read a t a temperature of 100" C. By placing weighed amounts of lamp black on filter papers of uniform textures, treat- ing them with equal volumes of the various solutions of alkali and soap, and weigh- ing the filter papers with the residue of lamp black which was not washed through, it was shown that solutions of the highest drop numbers would, under standard conditions, carry away the greatest amount of lamp black.Water, and the solutions of alkalis used without soap were unable to remove any of the lamp black. It was therefore concluded that solutions giving the highest drop number have the greatest detergent value with respect to unsaponifiable dirt.Alkaline solutions are thus in no sense detergents in the absence of free fatty acids or soaps. Ex- perimental results also show that, within the field examined, the greater the quantity of alkali added to the soap solution the better the detergent properties, the amount of alkali being limited in practice by the harmful effect on fabrics of large concen- trations of the hydroxyl ion; such effects being almost negligible in the case of sodium carbonate and cotton up to a 1 per cent.solution of sodium carbonate, provided careful rinsing be employed. This figure is from five to ten times the amount usually employed in power laundries. [Note by Abstractor.-No mention is made of the drop-number unit employed, but i t would appear to be the actual number of drops counted per unit volume of soap-alkali solution, small drops resulting in a large drop number and vice versa.] H. F. E. H.