SALTS SULPHATES. 



The foregoing process for pyrophorus, which is the usual one, is of 

 rather uncertain success, and the theoretical reasoning formerly given 

 respecting it being imperfect, I do not repeat it here ; but proceed to 

 state a better process, furnished me by Dr. Hare, and one which 

 rarely fails to succeed. 



Take lampblack 3 parts, calcined alum 4$ pearl ashes 8, mix them 

 thoroughly, and heat them for one hour, in a coated iron tube, to a 

 bright cherry red, or full red, but not to a white heat. Black's fur- 

 nace, filled with charcoal thoroughly ignited, the flues being then 

 shut, and when the fuel is half burnt down, again filled, and allow- 

 ed to burn quietly out, with the flues still cloesd, or nearly so, will 

 give a good pyrophorus. The tube must not be opened until it is 

 cold, and then very cautiously. The pyrophorus may be jarred out, 

 by inclining the tube, and gently striking it with a hammer. If good, 

 it fires on falling out, especially if the air is damp, or if breathed upon ; 

 caution should be observed lest the little explosions injure the eyes. 

 If a ramrod be introduced to detach the pyrophorus, the operator 

 should be on his guard, as a violent explosion sometimes happens, 

 discharging the whole contents at once, with a loud report.* This 

 pyrophorus fires brilliantly, if a large stream of oxygen gas be direct- 

 ed upon it from a gazometer, or if it be poured into oxygen, or 

 chlorine or nitric oxide gas. It fires also, if thrown upon water or 

 fuming nitrous acid . There can be little doubt that sulphuret of po- 

 tassium must be formed in this process, and that to potassium, in 

 some state or other, the principal phenomena must be attributed. 



(i.) All the, alkalies and soluble alkaline earths decompose this salt, 

 and if ammonia enter into its constitution, it is perceived by the odor r 

 when either of the other alkaline bodies is added and heat applied, 

 and by the cloud formed with the fuming acids. 



(/.) Jill the alkalies throw down the alumina; potassa and soda 

 redissolve it, if added in excess, and yield it up again if detached by 

 an acid. 



(k.) Ammonia precipitates the earth without redissolving it, or 

 only very slightly, and heat would throw down even this little. 



(I.) The soluble alkaline earths throw down a mixed precipitate, 

 of alumina and the earths, combined with the sulphuric acid. 



(m.) Baryta and strontia, are proper for the discovery of potassa; 

 if present, it would remain in solution, and could be detected by 

 muriate of platinum. 



(n.) The carbonates of alkalies decompose this salt, with a slight 

 effervescence at first, and throw down a carbonated earth. 



(0.) Crystals of alum are usually octahedral; 



* See Am. Jour, of Science, Vol. X, p. 366, and the same thing has often occur- 

 red to me since. 



