V 



of the Prussic, of the Ferruretted Chyazic, and of the Sulphuretted Chyazic* 

 Acids, and on that of their Salts; together with the application of the 

 Atomic theory to the analysis of these Bodies," Phil. Trans., 1815, p. 220 ; 

 " On the Anthrazothion of Von Grotthus, and on Sulphuretted Chyazic 

 Acid," Thomson's Annals of Philosophy, vol. xiii. (1819) p. 356 ; "On 

 the Triple Prussiate of Potash," Ann. Phil. vol. xii. p. 214, which contains 

 a discussion of his own analyses of "ferruretted chyazic acid," and that of 

 Dr. Thomson, published in a previous part of the same volume ; " On 

 Ferrochyazate of Potash, and on the Atomic weight of Iron," Ann. Phil, 

 vol. xiv. 1820, p. 205. 



In 1813 Mr. Porrett was engaged with Messrs. Wilson and Rupert Kirk 

 in an investigation of chloride of nitrogen, with a view chiefly to the ex- 

 amination of the physical properties and chemical composition of that 

 dangerously explosive compound, and the discovery of safe and suitable 

 processes for preparing it. 



In 1S16 he communicated to Thomson's Annals of Philosophy, vol. 

 viii. p. 74, an account of " Two Curious Galvanic Experiments," in which 

 he showed that a fluid is made to pass against gravity by the electric cur- 

 rent through a membrane from the positive to the negative pole when the 

 conducting wires of a battery are connected with water placed at different 

 levels on each side of the membrane. The fact so discovered by him is 

 by German writers generally associated with his name as " das Porrettsche 

 Phanomen." He also described the increase of action which is produced 

 in an exhausted voltaic battery by removing a portion of the fluid, whereby 

 the still moist plates are exposed to the action of the air. In 1817 he 

 made some " Observations on the Flame of a Candle," which were pub- 

 lished in the ' Annals of Philosophy,' vol. ix. p. 337. 



After an interval of twenty-six years, he again, in 1846, at the age of 

 sixty-three, took up chemical investigation, and contributed, in conjunction 

 with the late E. F. Teschemacher, a paper "On the Chemical Composition 

 of Gun Cotton" (Memoirs of the Chemical Society, vol viii. 1845-1848, 

 p. 258). His last paper " On the existence of a new Vegeto-Alkali in 

 Gun Cotton," for which he proposed the name of Lignia, was read before 

 the Chemical Society on December 21st of the same year, and is printed 

 in the Memoirs, vol. iii. p. 287. 



While devoting his leisure time principally to chemistry, Mr. Porrett 

 also occupied himself with antiquarian pursuits, especially the study of 

 ancient arms and armour, for which his residence in the Tower afforded 

 favourable opportunity. He retired from official duty in 1850, after a 

 service of 55 years. On that occasion his long and useful service was 

 honourably recognized by his superiors, and he received most gratifying 

 expressions of regard and attachment from his subordinate officers. He 

 was a Fellow of the Astronomical and Antiquarian Societies, and one of the 

 original members of the Chemical Society ; his election into the Royal Society 

 was in 1848. He died on the 25th November 1868, at the age of 85. 



