3 12 * An ANALYSIS of 



been filtrated, without danger of feparating any part of the fi- 

 liceous earth from the water by that operation. This is a con- 

 fequence of the fingular nature of the filiceous earth, feveral 

 properties of which, hitherto unnoticed, or not exactly defcribed, 

 I became acquainted with in the courfe of thefe experiments. 



We have no experience of the poflibility of diflblving this 

 earth in its concrete ftate by water alone ; but if it be diflblved 

 in water by means of an alkaline fait, although we afterwards 

 completely faturate the alkali with an acid, the earth thus fepa- 

 rated, provided there is enough of water, will not fubfide ; it 

 will remain diflblved ', the mixture will appear perfectly tranf- 

 parent, and will pafs through the nitre without the fmallefl 

 difficulty. To gr. iooo of the Geyzer water, I added more than 

 enough of acid to faturate the alkali. 1 then boiled the mix- 

 ture a little while, until a fmall part of it only was evaporated, 

 and I fet it afide in a quiet place. I know it contains a little 

 more than half a grain of filiceous earth ; but after ftanding 

 twelve months, there is not the fmallefl appearance of feparation, 

 the mixture is ftill perfectly tranfparent and fluid in every part 

 of it, though it be decidedly acid; and I know, that had it been 

 boiled down to a proper degree, a feparation of the filiceous 

 earth would have happened in a fhort time. I learned this by 

 another experiment with Rykum water. To gr. iooo of this 

 -water, I added a quantity of acid more than fufEcient for fa- 

 turating the alkali. The water was then boiled till it weighed 

 only 138 grains, and it was fet up in my clofet to remain un- 

 diflurbed. In about eight days, the tranfparency of it was a 

 little diminifhed, and afterwards there was a very flow fubfi- 

 dence of the matter which had produced this effect. It formed 

 gradually, at tht bottom, a ftratum of fome thicknefs, which 

 was a little lefs tranfparent than the clear water above, and was 

 thereby diftinguifhable from it. After a week or two more, I 

 poured off the clear water entirely, without difturbing the fedi- 

 ment, which was in fact a tender jelly, adhering to the bottom 



of 



