Magneiifnt.'^-^ Separation of iilctgnefta frm Clay. ;l^ 



together by tlie copper pieces marked a, b, z'-, b'. The pieces of contaft A, R, join the 

 ■op.pofite poles of the ri>agnets. 



Experience has fliewn me, that with an apparatus of this form, each part weighing 15 or 

 20lb. a force of 80 or 100 pounds will be required to feparate the pieces of Conta(Sl; and 

 that when an ordinary needle of the compafs ^s placed on the two- extremities of our two 

 compound bars, fig. 4J. they become magnetized to faturation without its being necefTary 

 to rub them with the u-pper pair of 'magnets.' It is fcarcely neceflary to obferve, that when 

 magnets of greater force are defired, it is neceffary, in proportion as the number of bars is 

 'increafed, to augment t-heirfeivgthatfo,' and the dimenfions of the parallelopipedonsof iron 

 ■which ferve for the armor. It would be eafy to afcertain the different dimenfions which 

 the magnets ought to have, in a manner fulEciently accurate for praclice, from the laws of 

 magnetifm, and the pofition ofthe centre of a£lioni df t-he bars of ft.eel,.of different lengths 

 and thiclcnefs, which we have explained in the "courfe of this memoir. 



On the Separation 9f Argillaceous Earth from Magtiefta. By Mr* F.jfccUM' . . 

 To Mr. N I,C Jft.OI^S.O.N. 



SIR, ... ■ ' .;;;; ; v" ; ^; ■'; . 



JL H E feparation 6f"arg{i[laceous' e^^h from magnefia, when both are combined in one 

 fubftance, as is very often the cafe in mineral bodies, has been hitTierto confidered as 

 one of the moft diflficult operations in the whole analyfis of artificial and natural com- 

 pounds. The experimental chemift, who is pra£tically employed in the invelligation of 

 mineral fubftances, mull be fenfible of the difficulties which unavoidably accompany the 

 prefent method of operation ; and muft likewife allow, that notvvithftanding the utmoft 

 care, accuracy and (kill, it is fcarcely poffible tp avoid uncertainty in his conclufions and 

 refults. For thefe reafons, I beg leave to obferve, that the above objeft may be accom- 

 pliflied to the utmoft precifion in the following manner : "When both thefe earths are in 

 a folution of muriatic acid in a perfeflly faturated ftate, the argillaceous earth may be 

 totally feparated by means of carbonate of ammoniac; as this will only difengage that earth, 

 and the magnefia will be retained in folution ; which may then be feparated by adding fo- 

 lution of pure potalh or foda to the remaining fluid. 



1 am, Sir, your humble fervant, 

 Haytnarhi, No. 17. FREDERICK ACCUM. 



M 2 VIII. Exiraas 



