of the Meteoric Stone of Concord. 355 



Chemical Composition. — So little of the mineral was at my 

 disposition without breaking the principal mass, that no other 

 qualitative examination was made than that with the blowpipe, 

 and this was the less important from the fact, that the pyrognostic 

 characters were so decisive as to the absence of all metallic oxyds. 

 All the fragments which could be found were carefully ground 

 in the diamond mortar and then in agate, and 390 millegrammes 

 of this powder were attacked by hydrofluoric acid, after the man- 

 ner recommended by Bunsen. When it was judged that all the 

 silica had been removed as hydrofluo-silicic acid, the residue was 

 dissolved in hydrochloric acid in the same platinum vessel in 

 which the attack was made by hydrofluoric acid. The absence 

 of alumina, iron, phosphoric acid, lime, &c, was easily ascer- 

 tained by the want of any reaction with ammonia and oxalate of 

 ammonia, which failed to produce any troubling in the solution 

 after addition of a sufficient quantity of chlorid of ammonium. 



Oxyd of mercury was next added to the boiling and concen- 

 trated solution, which was subsequently evaporated to dryness 

 ignited to expel the mercury, treated with pure hot water and 

 the magnesia, separated in this manner, from the double chlorid 

 of magnesium and mercury, was collected on a filter and weighed 



•0471 millegrammes. . . , 



The filtrate from the magnesia, which contained nothing but 

 alkaline chlorids, was evaporated in a platinum vessel of known 

 weight, and their quantity determined by the increase of weight 

 observed on repeated trials, with a constant result. 1 he alka- 

 line residue had the taste only of chlorid of sodium, it was dis- 

 solved and treated with bichlorid of platinum evaporated on 

 a water-bath to dryness, and treated with alcohol, ^o double 

 chlorid of potassium and platinum was obtained and the , on se- 

 quent purity of the chlorid of sodium was infer red The amount 

 of chlorid of sodium obtained was equivalent to 010b mm. 



The* weight of the meteorite employed = -390 grms. We 

 have found,— 



Magnesia, . . . -04H or 1|076 percent. 

 Soda, ... • '010b " W 18 



M 



■ • ■ 



«ow the known composition oi ieio»«*«~ ^ , . 



*, magnesia 12-98, and silica 87 02 per cent. =100. Ana 



composition of simple sil icate of soda, Na+2Si, is, of soda 40-37, 



a «d of silica 59-63 per cent. = 100. -mikfe* to 



Then 12-98 : 87^02: : 12-076 : 80-959 = the sihca requisite to 



form a tersilicate with the magnesia : f 



. And 40-37 : 59-63: :2-718 : 4014 the silica needed to term 



unpl 



