ON THE BORACIC ACID OP CENTRAL ITALY. 



30J 



Thus the seventh part of the imports from Tuscan provinces into Eng- 

 land, representing 80,000/. per annum, is derived from the evaporation of 

 mineral waters, an item second only in value to the celebrated oils of 

 Lucca and other parts of the country. 



Mr. Wood, of Stoke-upon-Trent, applied boracic acid to glazing pot- 

 tery in 1820, and for that branch of industry an enormous quantity is 

 consumed. 



The glaze for common English porcelain differs only from that 

 employed for figures and ornaments in the amount of borax: and silica. 

 Their respective composition is : — 



Felspar 

 Silica . 

 Borax 



45 — 45 | Flint Gla.-ss . . 20 — 20 



9 — 12 Nickel ... 4—4 



21 — 15 Minium . . . 12—12 



• — Dumas, Traite de Chimie, torn, ii., p. 265. 



With silicates of the alkalies and various metallic oxides, it forms 

 that beautiful and brilliant greenish-yellowish glass, made at Sevres, of 

 which the composition is given below : — 



Silica ..... 19-23 



Protoxide of lead . 57 '64 



Soda 3-08 



Boracic acid . . . 7 '00 



Peroxide of iron . . 6 '12 



Oxide of zinc . 

 Antimonic acid 

 Potash . . 



2'99 

 3'41 

 0'44 



100-00 



— Salvetat, Annales de Chimie. et de Physique, 3ieme Serie, torn. 15, p. 122. 



M. Mae's, of Clichy la Garenne, near Paris, manufactures glass of boro- 

 silicates of potash and zinc, boro-silicates of soda and zinc, and boro- 

 silicates of potash and baryta. 



I was informed by several persons that the vines in the neighbour- 

 hood of the lagoons do not get the Oidium disease, which may possibly 

 be attributable to the sulphurous vapours which arise so plentifully and 

 pervade the atmosphere — perhaps even in a less degree to the sulphur- 

 etted hydrogen ; hence this locality is well adapted for the growth of 

 vines, wherever the soil in the lower valleys admits of their cultivation. 

 May not this continual vapour of sulphurous acid account in some degree 

 for the excellence of the celebrated wines of Vesuvius ? For a similar 

 reason, it is possible that the superiority of the Canary wines may be 

 partly attributable to the sulphurous bath to which they are subjected, 

 as well to the richness of the soil, though that also is incontestable. 



[An article " On the Nitrate of Soda and Borate Districts of Peru," 

 by Wm. Bollaert, F.R.G.S., appeared in Vol. I. of the Technologist, 

 p. 115, and one "On the Uses of the Tincal of Asia and its Applica- 

 tions," by Arthur Robottom, p. 370 in the same volume. — Editor.] 



