718 PLUCKER ON THE DETERMINATION OF THE 



Thus we obtain the following numbers as representing the 

 attraction of the original solution of the protochloride of iron in 

 I. to IV. :— 



grms. grms. grms. grms. 



I. 3-94 — 0-40 =3-54 



II. 2-14 -0-40 + 0-06 =1-80 



III. 1-23 -0-40 + 0-09 =0-920 



IV. 0-72-0-40 + 0'105 =0-425. 



The attraction of I. is exactly eight times that of IV., and 

 in general the attraction is almost in proportion to the amount of 

 the magnetic substance. Assuming this proportionality as a 

 basis, if we calculate the attraction of IV. by dividing the sum 

 of the attractions by 15, and then calculate the attraction of the 

 other solutions, we have — 



The differences are so small that they fall within the limits of 

 errors of observation ; and thus it is confirmed that the attraction 

 of the solution of the protochloride is in proportion to the quantity 

 of the latter, presupposing that it is uniformly distributed through 

 the same space. 



9. In a second experiment, very finely divided iron was pro- 

 cured from a chemist's shop, and 



1-6 grm. 0-8 grm. 0-4 grm. 0-2 grm. O'l grm. 

 of it in each case triturated in a mortar with 25 grms. of fresh lard 

 until it formed a mass which was homogeneous in appearance. 

 We shall denote the five mixtures by I. II. III. IV. and V. The 

 watch-glass was first filled with pure lard, and was then attracted 

 by the electro-magnet, which was adjusted in exactly the same 

 manner as in the experiments detailed in the last paragraph, with 

 a force of 



0-25 grm. 



The watch-glass was then filled with each of the five mixtures in 

 succession, and the weight of the mixture in the watch-glass 

 (from which the amount of iron contained in it was calculated), 

 and lastly, the weight necessary to overcome the attraction of 

 the watch-glass were determined. By these means the following 

 results were obtained : — 



