fil.AGK SAND ON TH^ JtANKS OP THE pOIf. ig 



When a solution of pure mucous acid in boiling water is Mucous acid 

 gently evaporated to dryness, without separating the crys- heat!^^ ^ 

 tulline precipitate, that forms during the evaporation ; we 

 soon find, as soon as the whole of the liquid is wasted, that 

 the crystals grow yellow, then brown, and are converted into 

 a kind of viscid substance, tenacious, undergoing a sort of 

 fusion, and acquiring considerable hardness on cooling* 



The mucous acid, that has experienced this change, is Its properties 

 much more sour than usual, infinitely more soluble in '" *^^* ^'^** 

 water, and wholly soluble in alcohol, so that its properties 

 are in part altered. At first 1 thought, that I had converted 

 the mucous acid either into the malic, or the tartaric; but 

 the experiments I have made to verify this conjecture do not 

 yet appear to me sufficient, to authorise my advancing any 

 opinion respecting the nature of the change, that takes place 

 in the experiment I have described. 



III. 



Chemical Analysis of a Black Sand*, from the River Don, 

 in Aberdeenshire ; and of a Copper Ore, from Airthrey, in 

 Stirlingshire. By Thomas Thomson, M. Z). Lecturer 

 on Chemistry, Edinburgh f» 



T 



HE specimen, which formed the subject of the first of Black sand on- 

 the following analyses, was brought from the banks of the *!j^ tf"^^**^ 

 river Don, 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 1800, in order to ascertain its nature; but was too 

 little skilled at that time, both in mineralogy and practi- 



* For an account of a black Band, consisting of a ferriferous ore of 

 titanium, found on the bhores of Ligjria, and traced to the rock from 

 which it proceeded, see our Journal, vol. XXVI, p. 94. 



f Trans, of the Royal Soc- of Edinburgh for 1807, 



C 2 cal 



