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XVI. Chemical Analysis of a Black Sand, from the River 

 Dee, in Aberdeenshire* By Thomas Thomson, JW.D., 

 Lecture^' on Chemistry , Edinlurgh*. 



JL HE specimen which formed the subject of the first of the 

 following analyses was brought from the banks of the 

 river Dorr, about seven years ago, by my friend Mr. James 

 Mill, who at that time resided in Aberdeenshire. By him 

 I was informed that considerable quantities of it are found 

 in different parts of the bed- of that river, — that it is called 

 by the inhabitants iron-sand, — and that they use it for 

 sanding newly written paper. I tried some experiments in 

 the year 1 800, in order to ascertain its nature ; but was 

 too little skilled at that time, both in mineralogy and prac- 

 tical chemistry, to manage an analysis of any considerable 

 difficulty. 



The black powder is mixed with a good many small 

 whitish, reddish, and brownish grains, which, when ex- 

 amined by means of a glass, prove to be pieces of quartz, 

 felspar, and mica. From this it would appear, that the 

 sand of the river Dee consists chiefly of the detritus of gra- 

 nite or gneiss. 



When a magnet is passed over the sand, some of the 

 black grains adhere to it, and are by this means easily ob- 

 tained separate. But after all that can be attracted by the 

 magnet is removed, the greater part of the black powder 

 still remains. This residue is indeed attracted by a power- 

 ful magnet, but so very feebly, that it is not possible by 

 means of it to separate it from the grains of sand with 

 which it is mixed. Thus we learn, that the black matter 

 consists of two distinct substances ; one of which is power- 

 fully attracted by the magnet, the other not. As this se- 

 cond substance was obviously specifically heavier than the 

 grains of sand with which it was mixed, I placed a c^uan" 

 tity of the powder on an inclined plane, and by exposmg it 

 cautiously, and repeatedly, to a jet of water, T succeeded 

 in washing away most of the grains of sand> and thus ob- 

 tained it in a state of tolerable purity. 



The first of these minerals we may call iron-sand, and 

 the second iserine, as they belong to mineral species which 

 oryctognosts have distinguished by th^se names, 



I. Iron-Sand, 

 The iron sand is much smaller in quantity than the ise- 



• From Trai»4?tioji8 of Royal Society, Ediuburghj 1807, 



rine. 



