340 Chemical Society. 



" Thus the three first figures expressing the proportion of oxygen 

 contained in the air are constant, the fourth figure variable. I do 

 not consider, however, that the whole of this difference can arise 

 from errors of observation ; it is a subject requiring still further 

 examination. MM. Melloni and Piria are performing the same 

 experiments, at Naples, by the same means ; and also M. Stas, at 

 Brussels. M. Levy, who has assisted in the above experiments, in- 

 tends to repeat them in Denmark." 



M. Dumas urges the repetition of these experiments to be made 

 at various times and in various places all over the world, to -which 

 the English chemist has more easy access than others, in order to 

 resolve this curious physical problem. 



" The density of nitrogen appears to me," he adds, " to be be- 

 tween 0*970 and 0'973. That of oxygen, with which we have been 

 particularly occupied, and upon which we have made twenty dif- 

 ferent experiments, is always found comprised between ri05 and 

 1"108 ; it appears to be represented very nearly by ri06. That of 

 carbonic acid has varied between r526 and r528; if 75 is adopted 

 for the atom of carbon, then oxygen is condensed some thousandths 

 in forming carbonic acid. 



" Tlie density of hydrogen is always found above 0'0691, it has 

 varied between 0'0692 and 00696; we have operated on quanti- 

 ties of about 1 7 litres of this gas. As to the composition of water 

 by weight, M'hich has occupied me personally during nearly two 

 months, and on which I am still experimenting, I remain doubtful. 

 I have never found less than 12'50 for the equivalent of hydrogen, 

 and often 12'55, and at present I cannot choose between them. In 

 adopting the first of these numbers no error of any practical conse- 

 quence can result ; but as a philosophical question I take so high an 

 interest in it, that I shall continue my experiments until they leave 

 no doubt on the subject." 



" On the Analysis of Cetine and Ethal," by Dr. John Sten- 

 house. (See Memoirs, Vol. I., Art. 7.) 



" Notice on the Artificial Magnetic Oxide of Iron," by Thomas 

 Starkey Thomson, Esq. 



After adverting to the process given, in the last edition of Tur- 

 ner's Elements of Chemistry, for the preparation of the artificial 

 magnetic oxide of iron, the discovery of which is attributed to Abich 

 and Gregory, Mr. Thomson says, " Recollecting that this oxide 

 had been produced some years ago, by a process surprisingly similar 

 to that of Dr. Gregory, I corresponded with the inventor of it, Mr. 

 John Mercer, one of the original members of this Society, and part- 

 ner in the firm of Fort, Brothers and Co., calico-printers, from M'hose 

 letters I extract the following remarks : — ' This substance was pre- 

 pared by me in 1831, and in 1833 applied extensively as a medicine 

 •with great success. Mr. Gossage, of the Stoke Prior Alkali Works, 

 who was staying with me at that time for a few days, was so im- 

 pressed with its value as a medicine, that, upon his return home, he 

 wrote to me for a quantity of it to send to his friend Dr. .lephson of 

 Leamington, to whom I forwarded a quantity, with the receipt for its 

 preparation, and the dose. This receipt was published by Dr. Jephson 



