CHEMICAL AND PHYSICAL PAPERS. 55 



by Lehman ( Zeits. Phys. Chem. 5, 427). He suspended drops of 

 these substances in a medium of the same density, and found that 

 the drops had two axes, as in solid crystals. The drops were rounded 

 in form, but when two of these came in contact, instead of forming 

 one drop with only two axes, four axes still remained. Pressing drops 

 between glass plates did not destroy the axes, as might be expected. 



The study of other physical chemical properties of these crystalline 

 liquids has been carried on by Schenck. ( Zeits. Phys. Chem. 25, 

 337). He determined their density at different temperatures, and 

 found on platting the density curves that he obtained nearly straight 

 lines, with the exception that at the transition point the density 

 changes suddenly while the temperature remains constant, making a 

 jog in the curve. The curves for all the crystalline liquids known are 

 similar. 



The molecular weight of the substances in the two liquid phases 

 was found to be the same ; that is, there is no change in the size of 

 the molecules when the liquid passes through the transition point. 

 We must have, then, two liquids which are chemically identical, but 

 different in their physical properties, and, therefore, truly physical 

 isomers. A curve showing the relation of the different phases of one 

 of these substances could be drawn similar to the curve for sulphur. 

 Sulphur has one vapor, one liquid and two solid phases, the monoclinic 

 phase occupying a triangle (see Physical Chemistry, Walker), while 

 a crystalline liquid has one vapor, two liquid, and one solid phase, 

 the crystalline liquid phase occupying a triangle. 



Such peculiar properties seemed worth observing, so we decided to 

 make one of these substances. With the materials at hand, the prepa- 

 ration of ^-azoxyanisol promised the best results. The compound 

 from which ^-nitrophenetol was made by Gatterman is now on the 

 market, but as it could not be procured at once, it became necessary 

 to make it. The ^;-nitrophenetoi can be made (1) by treating ^-phe- 

 netol with fuming nitric acid (Hallock, Am. 1, 271), or (2) by boiling 

 j9-nitrochlorbenzene with alcoholic potassium hydroxide solution (C. 

 Willgerodt, Be. 15, 1002). The latter method was used. The j^-nitro- 

 chlorbenzene was prepared from chlorbenzene, and the chlorbenzene 

 from benzene itself. 



For the preparation of chlorbenzene, benzene was chlorinated in 

 the presence of aluminum turnings. The resultant liquid colored by 

 decomposition products, contained varying amounts of the chlorben- 

 zenes, which were separated by fraqtional distillation. The relative 

 amounts of the mono-chlorbenzenes depended upon the amount of 

 chlorine led into the benzene, and on the temperature during chlorina- 

 tion. The best results were obtained by warming the benzene until 



