Mr. C. Tomlinson on the Cohesion-Figures of Liquids. 355 



In order that the application of this subject to qualitative 

 analysis might be brought more directly before the attention of 

 persons who would value an easy and expeditious test, I read a 

 paper before the Pharmaceutical Society in February last, " On 

 the Verification of Castor Oil and Balsam of Copaiba by means of 

 their Cohesion-figures." These two liquids were selected to in- 

 troduce the subject of cohesion-figures in general, and its appli- 

 cation as a rough and ready test. The members were so much 

 interested in the subject that they requested me to furnish their 

 engraver with some figures for insertion in their journal, and 

 also to state what variations took place in the figure of castor oil 

 from various markets and of various growths. Accordingly I 

 examined twelve specimens of castor oil collected from different 

 sources, together with three or four specimens of balsam copaibse, 

 and wrote a report on the same, which will be found in the 

 Society's Journal*. 



In order to invite attention to the commercial oils, I read a 

 paper in March last before the Society of Arts, " On the Verifi- 

 cation of Olive-oil by means of its Cohesion-figure." The sub- 

 ject excited some interest and discussion f. 



In these communications I endeavoured to show that the co- 

 hesion-figure of the same substance is liable to certain variations 

 in different specimens, especially in the case of the oils, which 

 may be more or less viscid, more or less acidified or resinified. 

 1 do not here refer to the variations arising from adulteration 

 and admixture ; for this point is insisted on in all my papers. 

 But I was not unmindful of the changes likely to be induced by 

 age; for in my paper published in March 1862 (Philosophical 

 Magazine), I state that the cohesion-figure of the oil of lavender, 

 for example, may vary in different specimens, since it varies in 

 density from 0*87 to 094. The cohesion-figure of the oil of laven- 

 der is so striking that I was induced to try a number of speci- 

 mens in 1861, and in ail of them I obtained the peculiar Carra- 

 geen-moss pattern — unless, as was often the case, the specimen 

 had been adulterated with turpentine, in which case there was 

 no difficulty in detecting the adulteration. I also found that an 

 essential oil, entirely different from that of lavender in its pro- 

 perties and cohesion-figure, and also of less density, might be 

 made to give a somewhat similar cohesion-figure by dissolving a 

 small portion of camphor in it under a gentle heat, so as to bring 

 it to about the same density and texture as oil of lavender. I 

 stated in my first paper, that if two independent liquids could be 

 found of the same density and physical molecular constitution 

 (that is, equally fluid or viscid, &c), they would form the same 



* Pharmaceutical Journal for March and April 1864. 

 t Society of Arts Journal for March 4, 1864. 



