386 M. Stahlmann on the Action of Water on Lead. 



4. That the phosphorescence is only the result of the decom- 

 position of the colouring-matter, and does not belong to fluor- 

 spar itself. 



It is commonly assumed that only distilled water attacks lead, 

 but that saline water is without action. According to Stahl- 

 mann*, if such a water contains 0*00001 to 4 0018 per cent, of 

 NH 4 0, it attacks the lead, becomes active. With a percentage 

 of 0*0031 NH 4 and above, the water is again indifferent, and 

 no longer attacks the lead. If active water is boiled for an hour 

 and a half, the attack on the metal is considerably weaker. If 

 it is boiled with carbonate of baryta, it is all but indifferent. 

 An addition of 0*006 per cent, of nitric acid, and less, makes the 

 water active, any excess beyond that indifferent. Active water, 

 neutralized with small quantities of ammonia and nitric acid, re- 

 gained its former properties. 



The attack of active water on lead is connected with the access 

 of atmospheric air. Also in the presence of free carbonic acid 

 access of air is a hindrance to corrosion; on the other band, the 

 contact of water with air appears to be insufficient if the air is 

 free from carbonic acid. If a lead plate be placed in active water, 

 the corrosion of the plate starts preferably from the place where 

 the lead touches the bottom of the flask. When the lead was 

 suspended in active water, it remained unattacked for a week. 

 The precipitate was a hydrated carbonate of lead, the composition 

 of which varied. 



In the preparation of oxygen gas by the method of Fleitmann, 

 by the action of peroxide of cobalt upon bleaching-powderf, a 

 clear filtered solution is necessary ; for a turbid one, or a mixture 

 of chlorinated lime and water, froths up greatly and runs over. 

 According to Stolbe J, the tedious preparation of a clear solution 

 may, however, be avoided by adding to a thick magma of the 

 powder a few small pieces of paraffine. This melts on being 

 heated, and covers the paste with a layer which prevents any 

 frothing or rushing over. Instead of the peroxide of cobalt, 

 the author states that a small quantity of a solution of nitrate or 

 chloride of copper may be used, which, according to Bottger, 

 acts just like the salts of cobalt. The disengagement of gas 

 under these circumstances takes place very steadily and regularly. 



Chloride of thionyle was obtained by M. Schiff by the action 

 of dry sulphurous acid on perchloride of phosphorus, 



S0 2 + PCP = SO CI 2 + POCR 



Chloride of Oxychloride of 



thionyle. phosphorus. 



* Repertoire der Chemie, July 1866. 



t Phil. Mag. vol. xxx. p. 252. 



X Journal fur praJctische Chemie, July 1866. 



