14 SCIENCE PROGRESS 



The fibres were composed of hydrated neutral soap. Their 

 cross section was in nearly all cases ultramicroscopic, and those 

 of apparently macroscopic size were shown to be bundles of 

 fibres. The fibres were shorter in the case of potassium soaps, 

 and on standing these salts gave crystals, which were distin- 

 guished from the fibres by their higher melting-point. 



Surface Tension of Solutions of Fatty Acids. — Traube and 

 Somogyi first suggested the use of surface tension methods in 

 alkalimetry and acidimetry. A base which lowers the surface 

 tension of water may be used as an indicator in the titration 

 of an acid by a stronger but an inactive base. Windisch and 

 Dietrisch {Kolloid Zeitschrift, 1920, 26, 193), in the course of an 

 investigation into the suitability of the nonylic, caprinic, and 

 undecylic acids as indicators in acidimetry and alkalimetry, 

 found that solutions of these acids show anomalous properties. 

 A freshly made solution of undecylic acid in water gave a low 

 value for the surface tension, which increased to that of water 

 in the course of a few days. Addition of hydrochloric acid to 

 the freshly prepared solution produced a lowering of the sur- 

 face tension, which is not, however, permanent. After several 

 days the solution became cloudy and the surface tension rose 

 to that of water. The results were independent of the nature 

 of the containing vessel. The change in the activity of the 

 undecylic acid on addition of mineral acid was accompanied 

 by the appearance of colloidal particles visible in the ultra- 

 microscope, which finally became visible to the naked eye. The 

 authors conclude that the molecular disperse phase of the acids 

 is without influence on the surface tension of the water, whereas 

 the colloidal particles, visible in the ultramicroscope, are active. 

 On the other hand the coarse suspension is inactive. It is 

 suggested that both the active and inactive forms of the acids 

 occur simultaneously in aqueous solution. 



ORGANIC CHEMISTRY. By O. L. Brady. B.A., D.Sc. F.I.C., 

 University College, London. 



Baeyer's Strain Theory. — In a paper on the formation and 

 stability of spiro-compounds {Trans. Chem. Soc, 1920, 117, 1579) 

 Becker and Thorpe adduce further evidence in support of the 

 ideas enunciated in 191 5. 



In the earlier paper {Trans. Chem. Soc, 191 5, 107, 1080) 

 Beesley, Ingold, and Thorpe investigated the formation and 

 stability of spiro-compounds in the light of Baeyer's strain 

 theory. This theory stipulates that the normal angle (109° 30') 

 between the valency directions of the carbon atom has to be 

 altered to form the cyclohexane ring ; it is possible therefore 

 that the angles between the remaining valency directions will 

 be modified accordingly. If the two remaining valency 



