260 Intelligence and Miscellaneous Articles. 



dition of hydrochloric acid, be treated cold with excess of carbonate 

 of barytes and frequently stirred, and the liquor be filtered after twenty- 

 four hours, the washing water yields by evaporation a residue, which 

 gives traces of phosphoric acid on the addition of molybdate of am- 

 monia. If the insoluble residue be dissolved in hydrochloric acid, 

 after washing for some time, and the undissolved barytes be elimi- 

 nated, and if the phosphoric acid be precipitated in the state of am- 

 moniaco-magnesian phosphate, and if, lastly, the proportion of phos- 

 phoric acid be calculated from the calcined precipitate, a small loss 

 of phosphoric acid is incurred, but the result is very nearly accurate. 



When ammoniaco-magnesian phosphate is digested in a cold con- 

 centrated solution of borax, no phosphoric acid can be detected in 

 the filtered solution. If, then, a solution contain boracic and phos- 

 phoric acids, the latter may be separated from the former by preci- 

 pitating it in the state of ammoniaco-magnesian phosphate, especi- 

 ally when the solution contains no substances which are precipitable 

 by the addition of ammonia or magnesia. The precipitate contains 

 only a very minute portion of boracic acid. By this method, there- 

 fore, a little more phosplioric acid is obtained than ought to be ; but 

 this excess is about equal to the loss which results from the method 

 of using carbonate of barytes. 



The quantitative estimationof fluorine, when boracic acid is present, 

 is accompanied with insurmountable difficulties. If the solution be 

 acidified with nitric acid, and excess of carbonate of lime be then 

 added, and the mixture be heated and filtered, the undissolved por- 

 tion does not contain the whole of the fluoride of calcium correspond- 

 ing to the fluorine contained in the solution. A metallic fluoboruret 

 is formed, which, when treated with carbonate of lime, is not de- 

 composed, or only partially so. 



In insoluble combinations, boracic acid may be completely sepa- 

 rated from bases by fusing them with an excess of an alkaline car- 

 bonate. At least, by fusing borate of barytes and that of magnesia 

 with soda, and treating the mass with water, the greater part of the 

 base is obtained pure from boracic acid. — L'Institdt, Janvier 8, 1851. 



PHOSPHORESCENCE OF CHALK LINES. 

 To the Editors of the Philosophical Magazine and Journal. 



GE>fTLEMEN, 



The interesting paper of Professor Draper in this month's Num- 

 ber of your Magazine upon Phosphorescence, induces me to refer 

 to a means of obtaining phosphorescence that is difficult to recon- 

 cile with the Professor's hypothesis. The following are the ordinary 

 means of producing the phsenomenon, which I have not seen noticed 

 by other experimenters on that subject. Take a piece of chalk, 

 whiting, and I believe several other substances that will make a visi- 

 ble line, and draw a line upon a hot surface, such as a piece of iron 



