[ £53 ] 



XLVII. On the magnet' c Attract'wn of Oxides of Iron. 

 Bij Timothy Lane, Esq. F.R.S.''^ 



aIaving found, by experiment, that hardened iron is not 

 so readily attracted by the magnet as soft iron, and that 

 needles are inferior to iron wire as indexes to Six's thermo- 

 meter, I was proceeding to other comparative experiments 

 when f received the Second Part of last year's Philosophical 

 Transactions, in which I saw an Analysis of Magnetical 

 Pyrites, with Remarks on Suiphurets of Iron, by Mr. Hat- 

 chctt. 



This paper led me to examine what magnetical properties 

 iron possessed when free from inflammable matter. For 

 this purpose I obtained a precipitate of iron prepared and 

 sold at Apothecaries' Hall by the name oi' ferritni prcecipi- 

 taium. Mr. Moore, the chemical operator, informed me 

 that he prepared it by dissolving twelve pounds of sulphate 

 of iron in twenty-four gallons of distilled water, and then 

 adding eight ounces of sulphuric acid to render the solution 

 more complete. Twelve pounds of purified kali were mixed 

 with the solution : the precipitate was well washed with hot 

 distilled water, and then carefuUv dried. This precipitate 

 is similar to the sediment of chalybeate waters, and affords 

 no magnetic panicles; nor, when exposed to a continued 

 clear red heat, does it suffer any alteration beyond the ac- 

 quirement of a darker colour. Bat if any smoke or fiame 

 has access to it, then magnetic particles are evident. Heat,. 

 by the converging rays of the sun f, equal to that at which 

 glass melts, blackens the oxide, but does not render it 

 magnetic, if free from any inBan:mable matter. It is re- 

 quisite, in this experiment, to protect the oxide, by glass, 

 from the dust floating in the air, which otherwise will render 

 many of the particles magnetic. I attributed this effect to 

 the deoxidizing property oi' light, till, by employing a pro- 

 tecting glass, the result proved it to proceed from the dust 

 in the atmosphere. 



By repeated experiments I found that heat alone produced 

 no magnetic effect on the oxide, and that inflammable mat- 

 ter, with heat always rendered some of the particles magnetic. 



As the inflanmiable matter in C(jal had this effect, I mixed 

 some of the oxide with a portion of coal in a glass mortar,, 

 and continued rubbing them together for some time without 



• From the Tra^vsacltons nf the Roiial Society for 180'. 

 » f The lens employed in this experiment was twelve imhe'; in (!i;micti>r, 

 acd the heat at its focus was sullicieiu to melt iron ; from Mr.i)(jJlyB4- . :T 



any 



