648 [June 18, 



available for the preparation of rosaniline, was at one time disposed 

 to consider toluidine the true source of the so-called aniline-red. 



But toluidine the purity of which was established by combustion 

 when submitted under the most varied circumstances to the action 

 of the agents already mentioned, does not produce a trace of colouring 

 matter. The subject, which thus appeared to become more and 

 more obscure, was elucidated by a happy experiment. 



A mixture of pure aniline and pure toluidine, when heated with 

 mercuric chloride, stannic chloride, or with arsenic acid, instan- 

 taneously produced a magnificent red of most intense tinctorial power. 

 This experiment appears to show that the red belongs to both the 

 phenic and toluic series. 



I have not as yet pursued my researches further in the new field 

 opened by this experiment. 



In conclusion I may be allowed to state that by transforming into 

 oxalate commercial aniline, and especially a specimen of aniline 

 which was furnished to me by Mr. Nicholson as particularly well 

 adapted for the preparation of the red, I have been enabled to obtain 

 considerable quantities of toluidine in a state of perfect purity. 



Having thus at my disposal the necessary material, I hope soon to 

 acquire further experimental data for the explanation of the forma- 

 tion of rosaniline. 



IX. "On the Measurement of the Chemical Brightness of 

 various portions of the Sun's Disc." By HENRY ENFIELD 

 ROSCOE, B.A., F.R.S. Received June 12, 1863. 



The author has applied the method of measurement of the chemical 

 action of sunlight, which Professor Bunsen and he described in a 

 memoir presented to the Royal Society in November last*, to the 

 measurement of the chemical brightness of various portions of the 

 solar disc ; and although the observations which have as yet been 

 made are only preliminary, yet he thinks that the results obtained 

 are of sufficient interest to warrant his bringing them before the 

 Society. 



Secchi has shownj* that the calorific radiation of the centre of 



* Abstract, Proc. Roy. Soc. vol. xii. p. 306 ; Memoir, Phil. Trans. 1863. 

 t Astron. Nachr. Nos. 806, 833. 



