Chemistry and Physics. 



413 



dependent not on the actual quantity of colored material, but on the rel- 

 ative proportion of the solvent. Diagrams of the changing appearances 

 of sulphocyanid of iron, of chlorid of copper, and of chlorid of cobalt 

 were exhibited. 



13. On several new Methods of detecting Strychnia and Brucia ; Ex- 

 periments on Animals with Strychnia, and probable reasons for non-de- 

 tection of Strychnia in certain cases ; and a new method of instituting post- 

 mortem researches in Strychnia ; by Mr. T. Horsley, (Proc. Brit. Assoc., 

 Aug. 1856 ; Ath. No. 1503.)— In the first lecture, Mr. Horsley observed that 

 the circumstances attending Palmer's trial induced him to make a series 

 of experiments on the subject, and he tried the effects of a precipitant 

 formed of one part of bichromate of potash dissolved in fourteen parts 

 of water to which was afterwards added two parts in bulk of strong sul- 

 phuric acid. This being tried upon a solution of strychnine, the bulk was 

 entirely precipitated in the form of a beautiful golden-colored and insolu- 

 ble chromate. The experiment, as performed by Mr. Horsley, was very 

 interesting, and scarcely a trace of bitterness was left in the filtered 

 liquor. He did not claim to have originated this discovery of the use of 

 a chromic salt and an acid liquor ; but the point to which he called at- 

 tention was the essential difference in the mode of application, and he 

 maintained that it was as much out of the power of any human being to 

 define the limit of sensibility which he had attained, as it would be to 

 count the sands or to measure the drops of the ocean. Taking thirty 

 drops of a solution of strychnia containing half a grain, he diluted it with 

 four drams of water. He then dropped in six drops of a solution of bi- 

 chromate of potash, when crystals immediately formed, and decomposi- 

 tion was complete. Splitting up the half grain of strychnia into millions 

 of atoms of minute crystals, he said that each of these atoms, if they 

 could be separated, would as effectually demonstrate the chemical charac- 

 teristics of strychnia as though he had operated with a pound weight of 

 the same. He then showed the chemical reaction with those crystals. 

 Dropping a drop of liquor containing the chromate of strychnia into an 

 evaporating dish and shaking it together, he added a drop or two of 

 strong sulphuric acid, and showed the effect as previously noted. He 

 next showed the discoloration produced in chromate of strychnia and chro- 

 mate of brucia by sulphuric acid, the former being changed to a deep purple 

 and then to a violet and red. It had been asserted since the trial of Palmer 

 that the non-detection of strychnine in the body of John Parsons Cook 

 was owing to the antimony taken by the deceased having somewhat in- 

 terfered with the tests. Such a supposition was, in his (Mr. Horsley's) 

 opinion, absurd. Nothing, he considered, could more incontestably dis- 

 prove the fallacy than either of two new tests which he then per- 

 formed. These he considered double tests, because they had first the ob- 

 tainment of a peculiar crystalline compound of strychnine, which was af- 

 terwards made to develop the characteristic effects by which strychnine 

 is recognized. Mr. Horsley next related a series of experiments which he 

 •had made on animals with strychnine, and entered into the probable rea- 

 sons for its non-detection in certain cases, although (as he had just shown 

 before) a method of detecting infinitesimal quantities of strychnia by 

 tests. Having procured three rats at seven o'clock p. m., he (assisted by Dr> 



