from Saline Solutions. 281 



carbonate of lime is used, the result is modified according to 

 the strength of the acid in which the phosphate of lime is 

 dissolved. If it be very dilute, as when distilled vinegar is 

 employed, and calcspar in fragments be introduced, so as to 

 occasion a slow generation of carbonic acid, then little or no 

 phosphate of lime will be precipitated ; it will be kept in so- 

 lution by the carbonic acid, and so long as the carbonic acid 

 be retained ; but will be thrown down as soon as the gas 

 escapes, slowly and in part, for example, on exposure to the 

 air, — rapidly and entirely on the application of heat, so as 

 to expel the whole of the gas by ebullition. 



The effect of magnesia, and of carbonate of magnesia, or 

 phosphate of lime in solution is analogous. 



The introducing phosphate of lime thus, when treating of 

 earths, is not, I admit, perfectly exact ; I have been induced 

 to mention it, from certain resemblances which it bears to 

 the earths in its properties, and from the important part it 

 performs in organic nature, — a part depending on qualities 

 differing but little from those of the earths. 



Few and simple as these experiments are, the inferences 

 from them and their applications are not without interest. 

 If we consider what has been stated of alumine, how it is pre- 

 cipitated by lime and magnesia and their carbonates, ought 

 we to expect to find it in solution in the waters of the ocean, 

 or in any waters coming in contact with calcareous or mag- 

 nesian rocks ? Experience proves that we do not ; alumine 

 has never been detected in sea-water, or in any water ex- 

 posed to the action of the earths mentioned. I may add, the 

 circumstance that alumine has not the property of combin- 

 ing with and being rendered soluble by carbonic acid, seems 

 to be wisely designed, in conjunction with the manner in 

 which it is precipitated from its saline solutions, and in con- 

 junction with its peculiar quality of retaining moisture and 

 arresting water in its course ; properties which render it fit 

 specially for forming the basis of soils, and for entering into 

 the fissures of rocks, and by closing them, giving origin to 

 springs. 



If we consider also what has been mentioned of the oxide 

 of iron, as precipitated by the earths, and its relation to cap- 



