M. TECHNOLOGY. 535 



best paste with starch. By incorporating with the paste a 

 quantity of turpentine, equal in weight to half of the starch 

 employed, and stirring well while the paste is still hot, it will 

 be rendered more impervious to moisture, and at the same 

 time more adhesive. 25 (7, XXIL, 1874, 178. 



MIXTURE OF PLASTER OF PARIS W r ITH MARSH-MALLOW ROOT. 



An addition of two to four per cent, of powdered marsh-mal- 

 low root to plaster of Paris affords a mass that sets in about 

 an hour, and becomes so hard, when dry, that it may be sawed 

 and turned, and which is used for the manufacture of domi- 

 noes, dice, etc. With eight per cent, of the root a still hard- 

 er mass is obtained. It may be rolled into thin leaves, and 

 be painted, varnished, or polished. 13 C, April 1, 1874, 464. 



ENGLISH ENAMEL FOR CAST IRON. 



A brilliant, white, and very adhesive enamel is formed on 

 cast-iron articles in the following way. After heating them 

 to a red heat in sand, and keeping them at it for half an hour, 

 they are allowed to cool slowly, and are then carefully clean- 

 ed with hot dilute sulphuric or hydrochloric acid, rinsed with 

 water, and dried. A ground is next laid on by coating them 

 with the following mixture, afterward drying them at a high 

 temperature, and then heating them in separate muffles to 

 vitrification of the coating : 6 parts of flint-glass, 3 of borax, 

 1 of minium, 1 of oxide of zinc, mixed and finely pulverized, 

 and heated for four hours up to a red heat, and finally ren- 

 dered semi-fluid by increase of temperature ; after which the 

 mass is quickly quenched in cold water, and one part of it is 

 mixed with two parts of bone meal, and formed into a pap 

 by triturating finely with sufficient water. Upon this ground 

 the two following mixtures, prepared like the first, are then 

 laid in succession, the first of 32 parts of calcined bones, 16 

 of kaoline, 14 of feldspar, 4 of potash, stirred up with water, 

 dried, calcined, and suddenly cooled in water, and the pow- 

 dered mass triturated with water to a fine paste with 16 

 parts of flint-glass, 5^ of calcined bones, and 3 of calcined 

 quartz; after this has been put on and well dried, a second 

 coating is applied of 4 parts of feldspar, 4 of pure sand, 4 of 

 potash, 6 of borax, 1 of oxide of zinc, 1 of saltpetre, 1 of white 

 arsenic, 1 of the best chalk; these ingredients are mixed, cal- 



