392 Hydrogen gas apparatus. 



M. Wadell, who has seen this process practised in Chi- 

 na, has applied it successfullj to the preparation of zine 

 plates for galvanic apparatus. 



Bui, de la Soc. d^encour, 



28. Willis'' lute. — To prevent the materials contained in 

 earthen crucibles and retorts from penetrating through 

 their substance, the author prepares a lute composed 

 of two ounces of Borax dissolved in a pint of boiling wa- 

 ter, to which is added slacked lime in sufficient quantity to 

 form a soft paste. This lute applied to the vessel by a 

 brush within and without (if a crucible) vitrifies very 

 speedily, and prevents the penetration of the melted in- 

 gredients, but it cannot prevent the fracture of the vessel. 

 To accomplish this second object, the inventor covers re- 

 torts with a lute composed of linseed oil and slacked lime. 

 This is applied by a brush to retorts, and left to dry during 

 a day or two. It can be taken every time a retort is char- 

 ged to cover it with this lute, it may be used four or five 

 times without breaking. Cracks may be effectually stop- 

 ped by the same composition, only powdering the surface 

 with a little slacked lime. This may be done without risk 

 even when the retort is very hot. 



29. Hydrogen gas apparatus. — An instrument much 

 used in Germany and Russia, resembles the bottle of Gay 

 Lussac, except that the zinc is not suspended from the top, 

 but supported from the bottom on a tripod of lead, which 

 I's not att4»cked by the sulphuric acid. When the stopper 

 is opened, the gas escapes, the acid ascends and covers 

 the zinc and the action is renewed ; but as soon as the 

 acid touches the zinc, the lead which before produced no 

 change, furnishes on all sides a great quantity of little bub- 

 bles of gas, and more copiously than the zinc itself. This 

 results evidently from the galvanic action arising from the 

 contact of the zinc and lead ; but what is the most surpri- 

 sing is the prodigious effect of this pile of a single element, 

 compared with the weak effect of ordinary piles. 



Journal des mines. 



30. Method of discovering very Sfuall quantities of mer- 

 cury. — All the oxides and saline compounds of mercury, 

 placed upon gold in a drop of muriatic acid with a piece 



