Intelligence and Miscellaneous Articles. 243 



out needing any repair. To attain this, however, care must be be- 

 stowed on its preparation and application. 



Commercial zinc-white is mixed with half its volume, or an 

 equal weight, of fine sand, and rubbed in a mortar with solution of 

 chloride of zinc of 1*26, so as to form a homogeneous paste, which 

 is applied as quickly as possible. The weight of the solution re- 

 quired will be about the same as that of the oxide of zinc. 



If the solution is of this strength, there is time to apply it to the 

 vessel, and, on setting, it will have an adequate degree of hardness ; 

 with a greater degree of concentration, the hardening proceeds too 

 rapidly, while with a less the hardening is insufficient. The cork is 

 pressed a little in the neck of the apparatus, so that there is a hollow 

 space of 2 to 3 lines about the glass tube ; after moistening this 

 with the solution, it is filled up with cement, which is laid on a little 

 round the tube. Owing to the rapid hardening of the oxychloride, 

 the apparatus can be used a few minutes after. 



In disengaging chlorine, there is scarcely any annoyance from the 

 gas, so that a change of workmen is not necessary, as was formerly 

 the case. 



It may be used for many other purposes — cementing glass lutes 

 in metal tubes, closing slits in metal apparatus, &c. 



The cost is not great ; with less than an ounce of zinc-white, 

 and the same quantity of sand and of solution, a pretty large wash- 

 bottle may be made tight. — Zeitschrift fur Chemie, September 1867. 



EXPERIMENTS ON THE PERMEABILITY OF CAST IRON BY THE 

 GASES OF COMBUSTION. BY MM. H. SAINTE-CLAIRE DEVILLE 

 AND TROOST. 



General Morin has done us the honour of calling for an exact analy- 

 sis of the air which circulates round a strongly heated cast-iron stove. 

 We have found that this air contained considerable quantities of hy- 

 drogen and of carbonic oxide. This fact is completely explained by 

 the permeability to gases of cast iron at a high temperature, and by its 

 property of condensing carbonic oxide discovered by Mr. Graham. 

 It shows, moreover, that the air which is in contact with strongly 

 heated iron surfaces may become injurious to respiration. 



We proposed to ascertain whether the porosity of cast iron would 

 allow the gases of combustion to pass through the sides of cast-iron 

 stoves and to diffuse into the atmosphere of heated rooms. 



The principal part of the apparatus we used was a cast-iron stove, 

 resembling in shape those used in guard-rooms, and consisting of a 

 cylinder communicating with the exterior by two apertures, by one 

 of which air enters under the grate, while the other, which is in the 

 upper part, terminates in the stove-pipe. By the latter aperture is 

 introduced the combustible (coke, coal, or wood), which is received 

 on a grate at a suitable height above the lower aperture. 



The stove was raised successively to various temperatures between 

 red heat and bright redness. It is surrounded by a metal envelope 



R2 



