1819.] Scientific Intelligence. 14? 



plants which delight to vegetate in a thirsty soil. M. Damart 

 informs us that the cactus tuna, and other species of cactus 

 which vegetate in a similar soil in South America, produces 

 a gum of exactly the same properties with the gum of Bassora. 

 — (Jour, de Pharmacie, Ibid. p. 184.) 



VI. Sulphate of Lime. 



Some chemists have lately recommended the following method 

 of determining the quantity of lime in mineral waters : Throw 

 down the lime by oxalate of ammonia ; wash the precipitate^ 

 and diy it; expose it to a red heat in a platinum crucible, which 

 will convert it into carbonate of lime ; pour an excess of sulphuric 

 acid over this carbonate, evaporate to dryness, and expose the 

 dry mass to a red heat. It will now be sulphate of lime. Weigh 



it ; s-ftt- of the weight indicates the lime. 



This method may, perhaps, answer when the lime amounts 

 only to a grain or two ; but if its quantity amounts to 40 or 50 

 grains, or probably even to 15 or 20 grains, it is not possible to 

 combine the whole of it with sulphuric acid by a single process. 

 Hence the lime, when estimated in this way, will always be 

 below the truth. 



The simplest way to estimate the quantity of lime in oxalate 

 of lime is to expose the dry oxalate to a white heat in a platinum 

 crucible. By this process, it is converted into quick lime, and 

 nothing more is necessary than to weigh it in order to determine 

 its quantity. If an experimenter has not the means of producing 

 a sufficiently high temperature to reduce the oxalate to quick- 

 lime, he may proceed in the following way : Expose the oxalate 

 of lime to a red heat ; dissolve the carbonate of lime thus obtained 

 in muriatic acid ; add to the solution a quantity of liquid sulphate 

 of ammonia sufficient to decompose the whole muriate of lime 

 formed ; evaporate to dryness ; and keep the saline mass for 

 half an hour in a red heat. It is now pure sulphate of lime, from 

 which the quantity of lime may be determined. 



VII. Zircon. 



This mineral has been analyzed by Klaproth and Vauquelin, 

 and found by both of these chemists to be a compound of silica 

 and zirconia with a small portion of oxide of iron. Neither of 

 them noticed the presence of any alumina. I find, however, 

 that alumina is a constant ingredient. I analyzed a quantity of 

 crystallized zircons last winter by fusing them with thrice their 

 weight of potash, and treating the fused mass in the usual 

 manner. After separating the zirconia, I dissolved that earth 

 in sulphuric acid, and concentrated the solution, after adding to 

 it a certain quantity of sulphate of potash. This mass, which 

 was not quite liquid, but contained a mixture of sulphate of 

 zirconia in the state of a white powder, being set aside for some 



k 2 



