Intellwence a?id Miscellaneous Articles. 151 



"b 



the stronger, because he had found the equivalent of fluorine, de- 

 duced from the analysis of fluoride of lead, a higher number than 

 that obtained by the fluoride of calcium. M. Louyet had also an- 

 nounced his intention of studying and consequently of analysing all 

 the fluorides, in order to attempt a discovery of the cause of these dif- 

 ferences; the present notice gives the additional researches on this sub- 

 ject, and the author states his belief that he has decided the question. 



In a previous memoir M. Louyet had fixed the equivalent of fluo- 

 rine at 239"81 ; but this number ought to be raised to 240 in making 

 calculations with 250 for the equivalent of calcium and 200 for that 

 of sulphur. Calculation then indicated, if this calculation was cor- 

 rect, that 1 gramme of fluoride of sodium should yield 1'680 grm. 

 of anhydrous sulphate of soda. In decomposing this fluoride by 

 sulphuric acid, it is extremely difficult to avoid loss. The vapours 

 of sulphuric acid appear to carry off very small quantities of sulphate 

 of soda ; besides which it is requisite to expose the crucible for a 

 long time to a strong red heat, in order to completely decompose 

 the alkaline bisulphate formed. It is not useless to dwell on this 

 point, in order to show that all the sources of error tend to produce 

 loss ; that is to say, to lessen the weight of the sulphate obtained. 

 In three experiments, 1 gramme of fluoride of calcium gave succes- 

 sively 1*686, 1*685. 1683 of anhydrous sulphate of soda. All these 

 figures are higher than that which calculation indicates the equiva-* 

 lent of fluorine to be 240. 



These observations induced M. Louyet to repeat the analysis of 

 fluoride of calcium. A fresh series of experiments, which he con- 

 siders as exact as possible, gave him the following results : — In his 

 experiments 1 gramme of fluoride gave of sul])hate of lime, 1*742, 

 1-744, 1-745, 1-744, 1-7435, 1-7435, the mean being 1-7436. If 

 the equivalent of fluorine be taken as 237-50, that is to say, 19, 

 calculation shows that 1 gramme of fluoride of calcium should yield 

 1-74358 of sulphate of lime ; it results, therefore, from these experi- 

 ments, that the equivalent of fluorine is 237-50. 



M. Louyet has analysed other fluorides to verify this result. Fluo- 

 ride of barium converted into sulphate in a manner to ensure its per- 

 fect decomposition, gave the following results : — 1 gramme of the 

 fluoride of barium gave of sulphate of barytes 1-332, 1-331, 1-330; 

 the equivalent of fluorine being 237-50, the calculated amount would 

 be 1-33090. 



Lastly, the author repeated the examination of fluoride of lead, 

 and he discovered the cause of the diff^erences that had formerly re- 

 sulted between the equivalent deduced from the analysis, and that 

 obtained from the fluoride of calcium. He had not observed, that 

 on account of tjie great difference existing between the equivalents 

 of fluorine and lead, that the slightest error in the analysis would 

 lead to great diflferences in the calculated results. This being stated, 

 the following are the figures obtained in his last experiments : — 5 

 grammes of fluoride of lead gave of sulphate, 6-179, 6-178, 6-178 ; 

 the theoretical number is 6*1828. All these amounts are too small, 

 a circumstance which might readily arise from manipulation or other 

 causes which the author enumerates in his memoir. 



