Читать книгу Henley's Formulas, Recipes and Processes (Applied Chemistry) - Various - Страница 96
Lutes.
ОглавлениеLutes always consist of a menstruum and dissolved or suspended solids, and they must not be attacked by the gases and liquids coming in contact with them. In some cases the constituents of the lute react to form a more strongly adhering mass.
The conditions of application are, in brief:(a) Heating the composition to make it plastic until firmly fixed in place.(b) Heating the surfaces.(c) Applying the lute with water or a volatile solvent, which is allowed to volatilize.(d) Moistening the surfaces with water, oil, etc. (the menstruum of the lute itself).(e) Applying the lute in workable condition and the setting taking place by chemical reactions.(f) Setting by hydration.(g) Setting by oxidation.
These principles will be found to cover nearly all cases.
Joints should not be ill-fitting, depending upon the lute to do what the pipes or other parts of the apparatus should do. In most cases one part of the fitting should overlap the other, so as to make a small amount of the lute effective and to keep the parts of the apparatus rigid, as a luted joint is not supposed to be a particularly strong one, but rather one quickly applied, effective while in place and easily removed.
Very moderate amounts of the lute should be used, as large amounts are likely to develop cracks, be rubbed off, etc.
A classification may be given as follows:(1) Plaster of Paris.(2) Hydraulic cement.(3) Clay.(4) Lime.(5) Asphalt and pitch.(6) Rosin.(7) Rubber.(8) Linseed oil.(9) Casein and albumen.(10) Silicates of soda and oxychloride cements.(11) Flour and starch.(12) Miscellaneous, including core compounds.
I. Plaster of Paris is, of course, often used alone as a paste; which quickly {33} solidifies, for gas and wood distillation retorts, etc., and similar places where quickness of setting is requisite. It is more often, however, used with some fibrous material to give it greater strength. Asbestos is the most commonly used material of these, as it will stand a high temperature. When that is not so important, straw, plush trimmings, hair, etc., are used as binders, while broken stone, glass, and various mineral substances are used as fillers, but they do not add anything to the strength. These lutes seem to be particularly suitable for oil vapors and hydrocarbon gases.
Formulas:(1) Plaster and water.(2) Plaster (wet) and asbestos.(3) Plaster (wet) and straw.(4) Plaster (wet) and plush trimmings.(5) Plaster (wet) and hair.(6) Plaster (wet) and broken stone, etc.
II. Hydraulic Cement.—Cement is used either alone or with sand, asbestos, etc. These lutes are suitable for nitric acid. When used with substances such as rosin or sulphur, cement is probably employed because it is in such a fine state of division and used as a filler and not because of any powers of setting by hydration.
Formulas:(1) Cement—neat.(2) Cement and asbestos.(3) Cement and sand.
III. Clay.—This most frequently enters into the composition of lutes as a filler, but even then the very finely divided condition of certain grades renders it valuable, as it gives body to a liquid, such as linseed oil, which, unless stiffened, would be pervious to a gas, the clay in all cases being neutral. Thus, for luting pipes carrying chlorine, a stiff paste of clay and molasses has been suggested by Theo. Köller in Die Surrogate, but it soon gives way.
Formulas:(1) Clay and linseed oil.(2) Same, using fire clay.(3) Clay and molasses.
(1) Is suitable for steam, etc.; (2) for chlorine, and (3) for oil vapors.
IV. Lime is used in the old lute known as putty, which consists of caustic lime and linseed oil. Frequently the lime is replaced by chalk and china clay, but the lime should be, in part at least, caustic, so as to form a certain amount of lime soap. Lime is also used in silicate and casein compositions, which are very strong and useful, but will be described elsewhere.
Formulas:(1) Lime and boiled oil to stiff mass.(2) Clay, etc., boiled oil to stiff mass.
V. Asphalt and Pitch.—These substances are used in lutes somewhat interchangeably. As a rule, pitch makes the stronger lutes. Tar is sometimes used, but, because of the light oils and, frequently, water contained, it is not so good as either of the others.
Asphalt dissolved in benzol is very useful for uniting glass for photographic, microscopical, and other uses. Also for coating wood, concrete, etc., where the melted asphalt would be too thick to cover well. Benzol is the cheapest solvent that is satisfactory for this purpose, as the only one that is cheaper would be a petroleum naphtha, which does not dissolve all the constituents of the asphalt. For waterproofing wood, brick, concrete, etc., melted asphalt alone is much used, but when a little paraffine is added, it improves its waterproofing qualities, and in particular cases boiled oil is also added to advantage.
Formulas:
| 1. | Refined lake asphalt. | |
|---|---|---|
| 2. | Asphalt | 4 parts |
| Paraffine | 1 part | |
| 3. | Asphalt | 10 parts |
| Paraffine | 2 parts | |
| Boiled oil | 1 part |
Any of these may be thinned with hot benzol or toluol. Toluol is less volatile than benzol and about as cheap, if not cheaper, the straw-colored grades being about 24 cents per gallon.
Examples of so-called “stone cement” are:
| 4. | Pitch | 8 parts |
|---|---|---|
| Rosin | 6 parts | |
| Wax | 1 part | |
| Plaster | 1/4 to 1/2 part | |
| 5. | Pitch | 8 parts |
| Rosin | 7 parts | |
| Sulphur | 2 parts | |
| Stone powder | 1 part |
These compositions are used to unite slate slabs and stoneware for domestic, engineering, and chemical purposes. Various rosin and pitch mixtures are used for these purposes, and the proportions of these two ingredients are determined by the consistency desired. Sulphur and stone powder are added to prevent the formation of cracks, sulphur acting chemically and stone powder mechanically. {34} Where the lute would come in contact with acid or vapors of the same, limestone should not be the powder used, otherwise it is about the best. Wax is a useful ingredient to keep the composition from getting brittle with age.
A class of lutes under this general grouping that are much used are so-called “marine glues” (q. v.). They must be tough and elastic. When used for calking on a vessel they must expand and contract with the temperature and not crack or come loose.
Formulas:
| 6. | Pitch | 3 parts |
|---|---|---|
| Shellac | 2 parts | |
| Pure crude rubber | 1 part | |
| 7. | Pitch | 1 part |
| Shellac | 1 part | |
| Rubber substitute | 1 part |
These are used by melting over a burner.
VI. Rosin, Shellac, and Wax.—A strong cement, used as a stone cement, is:
| 1. | Rosin | 8 parts |
|---|---|---|
| Wax | 1 part | |
| Turpentine | 1 part |
It has little or no body, and is used in thin layers.
For nitric and hydrochloric acid vapors:
| 2. | Rosin | 1 part |
|---|---|---|
| Sulphur | 1 part | |
| Fire clay | 2 parts |
Sulphur gives great hardness and permanency to rosin lutes, but this composition is somewhat brittle.
Good waterproof lutes of this class are:
| 3. | Rosin | 1 part |
|---|---|---|
| Wax | 1 part | |
| Powdered stone | 2 parts | |
| 4. | Shellac | 5 parts |
| Wax | 1 part | |
| Turpentine | 1 part | |
| Chalk, etc. | 8 to 10 parts |
For a soft air-tight paste for ground-glass surfaces:
| 5. | Wax | 1 part |
|---|---|---|
| Vaseline | 1 part |
6. A strong cement, without body, for metals (other than copper or alloys of same), porcelain, and glass is made by letting 1 part of finely powdered shellac stand with 10 parts of ammonia water until solution is effected.
VII. Rubber.—Because of its toughness, elasticity, and resistance to alterative influences, rubber is a very useful constituent in lutes, but its price makes its use very limited.
Leather Cement.
| 1. | Asphalt | 1 part |
|---|---|---|
| Rosin | 1 part | |
| Gutta percha | 4 parts | |
| Carbon disulphide | 20 parts |
To stand acid vapors:
| 2. | Rubber | 1 part |
|---|---|---|
| Linseed oil | 3 parts | |
| Fire clay | 3 parts |
3. Plain Rubber Cement.—Cut the crude rubber in small pieces and then add the solvent. Carbon disulphide is the best, benzol good and much cheaper, but gasoline is probably most extensively used because of its cheapness.
4. To make corks and wood impervious to steam and water, soak them in a rubber solution as above; if it is desired to protect them from oil vapors, use glue composition. (See Section IX.)
VIII. Linseed Oil.—This is one of the most generally useful substances we have for luting purposes, if absorbed by a porous substance that is inert.
Formulas: 1. China clay of general utility for aqueous vapors.
Linseed oil of general utility for aqueous vapors.
2. Lime forming the well-known putty.
Linseed oil forming the well-known putty.
3. Red or white lead and linseed oil.
These mixtures become very strong when set and are best diluted with powdered glass, clay, or graphite. There are almost an endless number of lutes using metallic oxides and linseed oil. A very good one, not getting as hard as those containing lead, is:
4. Oxide of iron and linseed oil.
IX. Casein, Albumen, and Glue.—These, if properly made, become very tough and tenacious; they stand moderate heat and oil vapors, but not acid vapors.
| 1. | Finely powdered casein | 12 parts |
|---|---|---|
| Slaked lime (fresh) | 50 parts | |
| Fine sand | 50 parts | |
| Water to thick mush. |
A very strong cement which stands moderate heat is the following:
| 2. | Casein in very fine powder | 1 part |
|---|---|---|
| Rubbed up with silicate of soda | 3 parts |
A strong lute for general purposes, {35} which must be used promptly when made:
3. White of egg made into a paste with slaked lime.
A composition for soaking corks, wood, packing, etc., to render them impervious to oil vapors, is:
| Gelatine or good glue | 2 parts |
| Glycerine | 1/2 to 1 part |
| Water | 6 parts |
| Oil of wintergreen, etc., to keep from spoiling. |
X. Silicate of Oxychloride Cements.—For oil vapors, standing the highest heat:
1. A stiff paste of silicate of soda and asbestos.
Gaskets for superheated steam, retorts, furnaces, etc.:
2. Silicate of soda and powdered glass; dry the mixture and heat.
Not so strong, however, as the following:
| 3. | Silicate of soda | 50 parts |
|---|---|---|
| Asbestos | 15 parts | |
| Slaked lime | 10 parts |
Metal Cement:
| 4. | Silicate of soda | 1 part |
|---|---|---|
| Oxides of metal, such as zinc oxide; litharge, iron oxide, singly or mixed | 1 part |
Very hard and extra strong compositions:
| 5. | Zinc oxide | 2 parts |
|---|---|---|
| Zinc chloride | 1 part | |
| Water to make a paste. | ||
| 6. | Magnesium oxide | 2 parts |
| Magnesium chloride | 1 part | |
| Water to make a paste. |
XI. Flour and Starch Compositions.—
1. The well-known flaxseed poultice sets very tough, but does not stand water or condensed steam.
2. Flour and molasses, made by making a stiff composition of the two. This is an excellent lute to have at hand at all times for emergency use, etc.
3. Stiff paste of flour and strong zinc-chloride solution forms a more impervious lute, and is more permanent as a cement. This is good for most purposes, at ordinary temperature, where it would not be in contact with nitric-acid vapors or condensing steam.
4. A mixture of dextrine and fine sand makes a good composition, mainly used as core compound.
XII. Miscellaneous.—
| 1. | Litharge. | |
|---|---|---|
| Glycerine. |
Mixed to form a stiff paste, sets and becomes very hard and strong, and is very useful for inserting glass tubes, etc., in iron or brass.
For a high heat:
| 2. | Alumina | 1 part |
|---|---|---|
| Sand | 4 parts | |
| Slaked lime | 1 part | |
| Borax | 1/2 part | |
| Water sufficient. |
A class of mixtures that can be classified only according to their intended use are core compounds.
| I.— | Dextrine, about | 1 part |
|---|---|---|
| Sand, about | 10 parts | |
| With enough water to form a paste. |
II.—Powdered anthracite coal, with molasses to form a stiff paste.
| III.— | Rosin, partly saponified by soda lye | 1 part |
|---|---|---|
| Flour | 2 parts | |
| Sand (with sufficient water) | 4 parts |
(These proportions are approximate and the amount of sand can be increased for some purposes.)
| IV.— | Glue, powdered | 1 part |
|---|---|---|
| Flour | 4 parts | |
| Sand (with sufficient water) | 6 parts |
For some purposes the following mixture is used. It does not seem to be a gasket or a core compound:
| V.— | Oats (or wheat) ground | 25 parts |
|---|---|---|
| Glue, powdered | 6 parts | |
| Sal ammoniac | 1 part |
Paper read by Samuel S. Sadtler before the Franklin Institute.
