Colour of Substances and their Magnetic Properties. 213 



utmost facility to a magnet. The light-coloured oxide and fluoride 

 of zinc are magnetic only on the torsion balance ; the acetate of zinc 

 is colourless and diamagnetic ; when ignited a mixture of oxide and 

 sub-oxide remains, the darker particles of which are decidedly mag- 

 netic on paper. This is one of the simplest experiments for shewing 

 a magnetic product from non -magnetic elements, the pure acetate of 

 zinc can be so readily obtained, and only requires heating. Anti- 

 mony, like zinc, has magnetic oxides and fluorides of pale hue, both 

 of which, by fusing with borax, give darker-coloured partially-reduced 

 oxides, that move readily on paper to a magnet. The black 

 sulphuret also has particles of a similar description before any re- 

 duction of the sulphuret has been tried, but the effect is increased 

 when this compound has been subjected to a partial reduction. 



Potassium and Sodium, — These light-coloured metals are very 

 nearly inert on the torsion balance : this character likewise belongs 

 to their colourless oxides, fluorides, chlorides, and the numerous 

 white or transparent bodies into which they enter, and their dark- 

 coloured sulphurets are also of a similar nature. The only case I have 

 met with to the contrary is iron alum, already alluded to, where its 

 colourless nature is only adequate to subdue a portion of the mag- 

 netic tendency of the iron. 



Carbon, in the form of a pure diamond, is feebly attracted ; in 

 the finely-subdivided black state the attraction increases, and in the 

 coal left after the decomposition of colourless starch or sugar, there 

 is a great increase in the magnetic attraction, so much so, that I 

 had hopes of being able to move this carbon on paper ; but to do 

 so, I find that I must increase the energy of my test. The coal 

 from sugar is known to contain oxygen and hydrogen in combina- 

 tion, so that this kind of carbon resembles in composition the par- 

 tially-reduced products described as obtained from the diamagnetic 

 metals, while it also closely resembles them in attraction for the 

 magnet. 



Cadmium. — On the torsion balance this metal has a very slight 

 tendency to leave the magnet. Its carbonate is a pure snow-white 

 substance, possessed of no magnetic power — by heat it passes to 

 the oxide of a brick-red colour, accompanied by a rise in magnetic 

 force, just sufficient to make a few granules of the powder when 

 spread out move to a magnet underneath. The oxide of cadmium, 

 ignited with citric acid,* leaves a residue containing more magnetic 

 particles than the oxide reduced from the carbonate. In this case, 

 and frequently in these experiments, the use of an organic acid 

 which, during decomposition, furnishes carbon, is apparent. In the 

 destructive distillation of the acetate of lead, Berzelius states the 

 residue to be a carburet, a body which the experiments given have 



* This acid was tested for iron by ferro-cyanide of potassium, of which it 

 shewed not a trace. 



