248 . Intelligence and Miscellaneous Articles. 



nite ; but it seemed evident that if the outer armature becomes infi- 

 nitely large, its form becomes indifferent. We are thus led to admit 

 that when a sphere is placed in an envelope which is either infinite 

 or simply very large, the charge communicated to it by a given source 

 is proportional to its radius ; which amounts to saying in Coulomb's 

 language, that the thickness of the electric layer is inversely as its 

 radius. To verify this conclusion, I took four spheres of brass, the 

 diameters of which were 61'5, 90'5, 120, and 161 millims.; I placed 

 them successively on an insulating support in the centre of a very 

 narrow chamber, and charged them by connecting them with a con- 

 stant source by means of a metallic wire ; I then tested them by em- 

 ploying, as usual, a discharging electroscope. The charges obtained 

 were 5*2, 7-6, 11, and 14'7. The law of proportionality would 

 have given 5*2, 7*6, 10*1, and 13*6. These two series of numbers 

 are not identical ; but they differ so little, that we might expect 

 that the law of proportionality would be exactly verified in a larger 

 envelope. 



At first we might suppose that this law of proportionality is 

 opposed to one of the results obtained lty Coulomb ; but this con- 

 tradiction is only apparent. In Coulomb's experiments, in the case 

 of two unequal spheres, the spheres touched at the moment at which 

 they were electrified, and were only separated after being charged ; 

 their mutual action necessarily modifies the distribution of electricity. 

 The problem I have treated is quite different, and much simpler, as 

 the spheres on which I worked were only charged successively. — 

 Comptes Rendus, September 30, 1861. 



ON THE ACTION OF NITRATE OF SODIUM ON SULPHIDE OF SODIUM 

 AT DIFFERENT TEMPERATURES. BY DR. PH. PAULI, UNION 

 ALKALI WORKS, ST. HELENS. 



The mother-liquor obtained in the manufacture of soda-ash con- 

 tains, as is well known, large quantities of sulphide of sodium. In 

 ordert o oxidize that compound, nitrate of sodium is used. As long as 

 the boiling-point of the liquid is between 280° and 290° F., the sul- 

 phide is quietly oxidized to sulphate, nitrite of sodium being formed. 



But if the nitrate is added when the temperature of the boiling 

 liquid is about 310° F., a violent evolution of ammonia takes place, 

 according to the following equation : — 



2NaS + NaN0 6 + 4HO = 2NaS0 4 + NaH0 2 + NH 3 . 



As the liquor contains a large amount of sulphide, the quantity 

 of ammonia is so considerable that it may prove worth while to 

 connect the evaporating-pot with a tower filled with coke, over 

 which a stream of water or dilute acid is running. 



If the nitrate be added when the liquor has been heated to a tem- 

 perature much above 310°, a violent evolution of pure nitrogen occurs. 



5NaS+4NaN0 6 +4HO=5NaS0 4 +4NaQ 2 H + 4N. 



— From the Proceedings of the Literary and Philosophical Society 

 of Manchester, January 21, 1862. 





v.' 



