20
G-LASS.—White Bottle Glass.
well as those that follow, are calculated for 100 lbs.of sand:—
FOR CHAMPAGNE BOTTLES, ACCORDING TO JA1IKEL.
200 lbs. felspar.
20 “ lime.
15 “ common salt.
125 “ iron slag.
ORDINARY GREEN BOTTLE-GLASS.
72 lbs. lime.
280-278 “ lixiviated wood-ashes.
DARK GREEN BOTTLE-GLASS.
20 lbs. dry Glauber’s salt.
18 “ soap-boilers’ flux.
1 “ Scheffel—Pruss.—lixiviated ash.
30 “ glass from the hearth.
170 “ green cullet or broken glass.
45 ** basalt.
White Bottle or Chemical Glass. —Under thishead may be included white glass for medicinal bottlesand chemical purposes, refractory Bohemian glass fortubing, &c., and foreign crown. The most beautifulmaterial for bottles is furnished by flint-glass or crystal,but these are only intended for ornamental articlesor vessels for the table, and will be alluded to underFlint-glass.
The general character of white bottle-glass consistsin this, that it is composed of purer materials thanthe green; decoloring matters are used, and thematerials are selected as free from iron and aluminaas possible. Moreover, in this case the glass is sub-jected to a thorough fining process. The followingare general standards of composition for differentvarieties of glass of this description :—
foe apothecaries’ piiials.
100 lbs. white sand.
30- 26 “ potash—impure.
17 “ lime.
110-120 “ ashes.
•25--5 “ binoxide of manganese—cullet.
BOHEMIAN CRYSTAL FOIi GEINL'INQ.
100 lbs. white sand.
0-60 “ purified potash.
8 “ chalk.
40 “ broken glass.
•75 “ manganese.
SEMI-WHITE.
100 lbs. sand.
100 “ crude soda, containing lime.
100 “ cullet.
•5- 1 “ manganese.
100 lbs. sand.
30 “ potash.
18 “ lime.
decoloring matters.
CLEAR WHITE.
100 lbs. sand.
65 “ calcined potash.
6 “ fallen lime.
100 “ white cullet.
*5 “ manganese.
WHITE GLASS FOE CHEMICAL PURPOSES.
100 lbs. white sand.
41‘4 “ potash.
17-5 “ lime.
Bohemian Glass. —The coarser qualities of thiskind of glass are analogous in composition to bottle-
glass, and are distinguished by comparative freedomfrom colour, great lightness, and their very refractorynature, which renders them capable of resisting notonly high heats, but sudden changes of temperature.Hence the value of this glass for chemical purposes,sueli as tubing, retorts, &c. Its lightness, and thealmost total absence of colour, cause it to be highlyvalued on the Continent for table-ware, where it isalso employed to make costly windows, for coveringengravings, &c. In common with crown-glass, it isalso peculiarly fit for optical instruments, in which itis employed to achromatize the flint-glass. Theseremarks apply to the finer qualities, for whichDumas gives the following choice of proportions:—
Quartz in powder, or fine silicious sand, f 1AA 11A - 1AA
washed with hydrochloric acid,.f U0 110 100
Purified carbonate of potash,. 60 64 66 75
Very pure carbonate of lime,. 20 24 25 50
In a Bohemian glass of old manufacture, Dumasfound
Alumina,. 9-6 = 4'48) 9'04
Lime, . 9*2 = 2-57 v oxygen of
Potash,. 11-8= 1-99} the bases,
which would give exactly the proportion of 1 : 4between the oxygen of the bases and that of theacid. On the whole, Bohemian glass may be describedas a silicate of potash and lime, with a small pro-portion of alumina, magnesia, and other ingredients.This will be obvious from the following analysis of aglass, taken by M. Perdonnet from a manufactoryat Neuvelt, and analyzed by M. Gros in the labora-tory of the School of Mines at Paris :—
Lime,. 10-0 = 2*81
Potash,. 11-0 = 1-86
Alumina,. 2-2 — 1-02 . _
Magnesia,. 2*3 = 0*89 ‘
Oxide of iron,. 3-9 = 1*20
Oxide of manganese. 0-2 — 0-05_
101-2
Here it will be noted, that the silica contains aboutfive times the aggregate oxygen of the bases. Itwill be observed also, that in Bohemian glass potashtakes the place of soda.
Foreign Crown-Glass.—T he name of crown-glassis limited in this country to that which is formedinto circular plates by the process of blowing; butthe crown-glass of the Bohemian glass-houses isgenerally moulded into different shapes, with a viewto grinding and polishing. Kegarded in this light,the foreign crown, properly so called, is rather dis-tinguished by its composition than by the methodsof manipulation adopted in its manufacture. Likethe coarser Bohemian glass, it is a silicate of potashand lime; whereas, in the Engisli crown, soda isemployed, either in the shape of sulphate or carbon-ate. Dumas analyzed a good crown-glass of Germanmanufacture with the following result:—
Ceutesimally. Oxygen.
Silica,.62-8 r= 32-6
Alumina, oxide of iron and of manganese, 2'6 = 1 ‘ 3 T
Potash,.22-1 — 37 J