A preparation for writing on glass called "Diamond Ink" is made by mixing barium sulphate, three parts; ammonium fluoride, one part; and sulphuric acid a quantity sufficient for decomposing the ammonium fluoride, and making the mixture of a semi-fluid consistency. The mixture should be prepared in a leaden dish, and is best kept in a gutta percha or a leaden bottle. It is to be used with a common pen, and at once etches a rough surface on the parts of the bottle it comes in contact with.

Action of Water, Acids and Alkalies; Poor Bottles Easily At-tacked. - Water at ordinary temperature and under ordinary contact with glass has but a slight or no perceptible effect. An increase of temperature and of surface of contact, however, tends to augment the dissolving action of water. The composition of glass has a manifest influence upon its solubility. Where glass contains an excess of alkali it is more apt to be altered by the action of water, while glass containing a predominant earthy silicate is freer from attack. A peculiar purple coloration is often noticed in panes of glass in .places exposed to dampness. This is explained by the action of water being in contact with the surface of glass for more or less time, producing a solvent action upon the alkali contained in the glass. If the surface of such a glass is rubbed, small thin pellicles will be detached; they are composed of earthy silicates, the alkaline silicate having disappeared. When the action is continued for a long period, the peculiar iridescent coloration increases. According to Newton, this coloration is the result of the reflection of light upon the thin pellicles or pieces which become somewhat separated from the main body of the glass. The following analysis shows plainly the action of water upon glass:

Part remain-ing intact.

Part having been altered

Silica................................

59.2

48.8

Alumina..............................

5.6

3.4

Lime ................................

7.0

11.3

Magnesia..............................

1.0

6.8

Oxide of iron............................

2.5

11.3

Soda.................................

21.7

0.0

Potash..............................

3.0

0.0

Water...............................

0.9

19.3

100.00

100.9

All glass when reduced to powder is subject to the influence of water, and gradually absorbs carbonic acid in such a quantity as to show quite an effervescence in contact with acids. Powdered glass boiled in water in contact with carbonic acid absorbs this gas in a few minutes and produces an instantaneous effervescence in acids. Powdered glass kept in boiling water for several hours with sulphate of lime produces a notable quantity of sulphate of soda. All glasses reduced to powder will bring back the blue color of test papers colored red; it is owing to their alteration by the absorption of water. Glass made with soda is subjected to a different alteration from that made with potash.

Soda glass continues to become iridescent with time, sometimes to such an extent as to appear to be colored glass, and small pellicles gradually become detached. The same peculiarity has been noticed in ancient glass dug from the earth, and the iridescent coloration is attributed to decomposition by water. Potash glass is affected by water in producing small crystals upon its surface. This deposit of crystals depolishes glass, renders it rough, and seems to have covered the surface with a multitude of small cracks. These cracks appear to be the result of the small crystals acting upon the surface of the glass in a manner similar to that of cutting with a diamond. Flint and crown glass, for the particular purposes they are intended, are manufactured with a large proportion of alkalies. This excess has the tendency to make them damp on the surface, to make them lose their transparency, and, with time, to alter their shape. Crown glass disks, piled one upon another, have been known to become cemented quite firmly together; this is caused by the silicate of potash they contain in excessive quantity attracting the dampness of the atmosphere.

To illustrate the action of water upon glass under pressure and temperature, some glass tubes were taken and subjected to a temperature of 572 degrees in contact with water. The result transformed the glass into a fibrous matter resembling Wallastonite (silicate of lime). Ordinary flint glass is affected by long boiling in water. Thus it will be seen that manufacturers who may be tempted to produce glass with an excess of alkali, in order to save fuel in melting, are exposed to produce an inferior quality, which, after a comparatively short time, will show the peculiar objectionable iridescent coloration. This coloration, however much prized in fancy articles, is very obnoxious in window and plate glass. Glasses made of silica and alkali alone are incapable of permanently resisting the action of water. The addition of lime or oxide of lead appears to be necessary to give them this quality. Pulverized glass in contact with hydrochloric acid diluted with hot water, or even at ordinary temperature, is easily attacked. The same effect takes place with lead glass, the dissolution being in contact with hydrosulphuric acid.

Bottle glass being made with a large proportion of bases, in order to produce a cheap glass, is very easily attacked by acids. If a bottle is filled with strong sulphuric acid, after a certain time small concretions of sulphate of lime will appear, while alumina and the alkali will be dissolved in the acid. Silica will fall to the bottom in the form of a jelly. Many bottles are attacked by the concentrated mineral acids, but resist the action of these acids diluted. Some bottles are even attacked by the bitartrate contained in wine, and decompose it and impart to it the taste of ink, also destroying its color. It has been ascertained that few bottles, if even made of a superior quality of glass, resist the action of wine in course of time. The discoloration of wines is attributed to the formation of a lake made up of gelatinous silica and the coloring matter of wine. Certain white wines will sometimes turn black when exposed to the air even for a few moments. These wines contain tannin, which, under the influence of a small quantity of iron extracted from the glass when exposed to the air, form a trace of tannate of peroxide of iron, the coloring matter of ink.

Certain bottles are rapidly attacked by acid liquors. Champagne bottles of apparently good manufacture have been known to alter the color of wine in a few days. Acidulated water, containing only four per cent, of sulphuric acid, has also been known to produce even in one day a thick crust of sulphate of lime and a dissolution of sulphate of iron and potash. In making experiments of this nature glass was found to contain -

Silica .......................................

54.56

Lime ........................................

18.20

Alumina .....................................

10.43

Protoxide of iron ................................

1.86

Magnesia ......................................

0.51

Potash .........................................

1.37

Soda ..........................................

13.07

100.00

The number of bases contained in this glass explain the rapid effect that even the weakest acids produce upon wine.

Flint or lead glass resists much better the action of water and acids. Strong alkaline solutions preserved in lead glass bottles extract oxide of lead. These alkaline sulphates in course of time become thoroughly cemented. This is owing to the formation of a soluble alkaline silicate, which has very strong adhesive qualities. Bottles intended to contain re-agents should be made of a hard glass, free from lead. A study of the matters derived from glass by the effect of the solutions used should also be carefully made to avoid erroneous results in making analysis. Hydrofluoric acid having a very strong dissolving effect upon glass, this quality is availed of for engraving glass and for making easy and reliable analyses of all kinds of glass. Hydrofluoric acid is made by introducing into a leaden still pulverized fluoride of calcium and concentrated sulphuric acid. The mixture is heated and the distillate is received in a leaden receptacle containing water. To manufacture this acid in large quantities a cast-iron still is substituted for lead. The acid is kept in gutta-percha or leaden bottles. It should be handled with great care, for if any of it should penetrate through the skin by an abrasion or a cut, it produces painful sores which are difficult to cure. Rubber gloves should be used when it is handled.