Glass is an amorphous hard, brittle, super cooled liquid. It is not a true solid.
Chemically glass is a mixture of number of silicates and has no definite formula. But the general composition can be represented as `xM_2O · yM'O·6SiO_2` where `M` is monovalent alkali metal ,like `Na, K,` etc., `M` is a bivalent metal like `Zn, Pb` etc., and `x, y` are whole numbers. Silica is the major constituent of all glasses.
`=>` Glass is a mixture and not a compound.
`=>` Glass is known as super cooled liquid with no sharp melting and boiling point.
`=>` Glass is chemically inert towards a lot of chemicals.
`=>` Glass stoppers should not be used in containers of `NaOH` or `KOH.`
`=>` Glass is soluble in `HF` due to formation of `H_2SiF_6` . Therefore, `HF` solution is used for etching of glass.
`text(Raw Material) : `
Raw material used for the manufacture of glass are :
(i) Silica `(SiO_2)` and cullet (glass pieces)
(ii) Compounds of alkali metals e.g. `Na_2CO_3, NaNO_3 , K_2CO_3 , KNO_3 , Na_2SO_4` and `K_2SO_4.`
(iii) Compounds of alkaline earth metals `CaCO_3 , BaCO_3 , CaO`.
(iv) Oxides of heavy metals e.g. `PbO , Pb_3O_4`.
`text(Coloured Glass) : `
These are prepared by mixing colour supplying substances in the molten or fused state of glass. Such substances are tabulated below
Colour producing substance and their colour
Substance Used | Colour of Glass |
---|---|
Cuprous oxide | Red |
Cupric oxide | Peacock blue |
Potassium dichromate | Green or greenish yellow |
Ferrous oxide | Green |
Ferric oxide | Brown |
Manganese dioxide | Light pink, in excess black |
Cobalt oxide | Blue |
Gold chloride | Ruby red |
Cadmium sulphide | Yellow |
Carbon | Amber colour (brownish black) |
Slow cooling of glass is called annealing of glass. Since while preparing glass is at a very high temperature if it is cooled suddenly, glass being a bad conductor of heat, its upper layer cools down while interior portion remains in a state of strain, due to this unequal expansion glass cracks into pieces. To avoid this, glass is cooled slowly. This slow cooling is called as annealing of glass.
Types of Glasses, their Properties and uses
Types of Glasses | Properties | Uses |
---|---|---|
Soda glass or soft glass | Contains sodium carbonate, calciurn carbonate and silica. brittle and cheapest | Window glass, bottles dishes, tubelights. domestic utensils etc |
Potash glass or hard glass | Contains carbonate of K. Ca and silica, high temperature resistant. | Hard boiling glass test tubes. beakers, etc |
Photochrornatic glass | Turns dark in sun li[Jht because of the presence of embedded microcrystalline silver compound (silver chloride) in glass | Eye lenses and goggles |
Pyrex glass (borcsilicate glass) | Contains borax and silica. withstand sudden alterations in temperature | Laboratory equipments |
Flint glass | Contains sodium, potassium and lead silicate. have high refractive index | Optical instruments like lens cf camera, prisms. microscopes, telescope and in electric bulbs |
Crown glass | Contains oxides of potassium, barium and silicon, have high refractive index | Optical instruments |
Jena glass (best form of glass) | Soft, strong and more resistant to acids and alkalies. contains zinc and barium borosilicate. | Bottles for keeping acids and alkalies in laboratory |
Crook's glass | Contains cerium oxicle (`CeO_2`,) and silica. thus. absorbs UV rays. | Eye tenses used in different eye defects |
Lead crystal glass | Contains potassium carbonate. lead oxide and silica, shows optical phenomenon of total internal reflection. | Various omamental items, costly glass containers |
Quartz glass' or silica glass | Ultraviolet rays emerge out through it. | In rnaking bulb of ultraviolet amp, laboratory equipments |
The knowledge of ink was known before 4000 years in Egypt. First time ink was prepared from coal and resin. Ink is a colloidal system of fine pigment particles dispersed in a solvent. The pigment may or may not be coloured, and the solvent may be aqueous or organic. On the basis of preparation, ink is of two types
(i) Aniline ink and (ii) Iron gel ink
`text(Raw Material for Aniline Ink) : `
The important raw materials used for the manufacture of aniline ink are as follows :
`=>` Eosin, glycerine, carbonic acid, phenol.
`=>` Carbonic acid `(H_2CO_3)` and boric acid `( H_3 BO_3)` to prevent the production of fungi in ink, thus used as fungicide
`=>` Glycerine is used in manufacturing the stamp pad ink.
`=>` Resin or glue or gum for shine.
Colours of Ink due to Different Substances
Colour of ink | Colouring substance |
---|---|
Black-blue ink | Naphthalene black |
Blue colour | Methylene blue |
Red colour | Eosine and congo red |
Green colour | Malachite green |
Black colour | Aniline black |
`text(Raw Material for Iron Gel Ink) : `
The important raw material used for the manufacture of iron gel ink are as follows :
`=>` Resin or glue or gum arabic, glycerine.
`=>` Alcohol or spirit or phenol.
`=>` Tannic acid and galic acid used in blue-black ink.
`=>` Ferrous sulphate (`FeSO_4`) and dilute hydrochloric acid (`HCl`) are main constituents of this ink.