498 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



lead loses it lie very near each other. The most favorable 

 temperature for the formation of red-lead is that approaching 

 a dull red heat, without, however, reaching it. Mercier has 

 lately constructed a furnace, for use on a large scale, for the 

 manufacture of red-lead, which takes into account these con- 

 siderations. It is essentially a large muffle, around which 

 the fire plays in a great number of small channels, and by 

 means of dampers the heat is easily regulated. By this fur- 

 nace, in full action and continuously worked, about four tons 

 of red-lead may be produced in twenty-four hours. 21 A, 

 February, 1872,182. 



PROTECTING ZINC AGAINST ACID. 



The action of dilute sulphuric acid upon zinc, resulting in 

 the production of bubbles of hydrogen, can, it is said, be im- 

 mediately stopped by introducing a small quantity of etheri- 

 al oil, such as lavender, turpentine, etc. The evolution of hy- 

 drogen begins again, however, if a certain quantity of alco- 

 hol is added to the liquids. The action of the oil consists, 

 probably, in forming a thin protecting film upon the zinc. 

 8 C\ February 1, 1872, 39. 



BUTTONS, ETC., FROM SOAP-STONE. 



Buttons, dominoes, and other small objects requiring great 

 hardness are now manufactured in Germany from soap-stone 

 by grinding refuse chips and fragments to powder, mixing 

 this with water-glass in a tub, and, after allowing it to stand 

 for some hours, drying it upon a plate and then grinding it 

 again to a fine powder. When thus prepared, this powder 

 is to be brought under a powerful press, where the desired 

 shape is given, and the objects are then to be baked in fire- 

 proof crucibles, kept air-tight, and after burning, immersed 

 again in water-glass until they are completely saturated ; aft- 

 er this they are again dried and again heated in a closed cru- 

 cible. By repeating this operation several times the objects 

 can be made to possess any required degree of hardness. 

 They are then to be cleaned off by placing them in water in 

 a rapidly rotating tub, and afterward dried and introduced 

 into a second rotating tub, with soap-stone powder, which 

 will give them the proper degree of finish. Bayerisches In- 

 dustrie- unci Gewerbe-Blatt, December, 1871, 340. 



