Acid-proof - (9) See (1). This cement is not at all attacked by hydrochloric, and but very little by nitric acid. When heated it softens but very little. It does not easily dry upon the surface. If this cement is mixed with 1/5 of its weight of litharge, or minium, it dries up in the course of time, and becomes hard. This is known as " Ben-icke's Cement."
(10) A luting which will resist acid vapours and chlorine, even at a high temperature, and is thus applicable to chlorine and hydrochloric apparatus, may be prepared by mixing three parts by weight of fine dry clay with one part by weight of the residue left from the distillation of glycerine. This mixture does not loso its plastic properties even at a high temperature, but is not suited for use where it might be exposed to atmospheric changes, since the glycerine which it contains absorbs moisture. Hence it should be prepared immediately before use.
(12) The balsam of Tolu, which has been used for preparing the syrup, has hitherto been utilised only in making a varnish for pills, and it therefore accumulates in course of time to a considerable extent. A composition useful as bottling wax may be prepared by stirring into the melted balsam one-tenth its weight of levigated bole. It sets quickly, with a fine glossy surface, and is less brittle than the wax generally employed. A mixture of residual balsam, amber resin, of each four parts; Venice turpentine, vermilion, of each 1 part; melted together and well stirred, forms sealing-wax of very fair quality.
(10) Soulan's. Make the following solution: - Purified resin, 7 dr.; ether, 10 dr.; collodion, 15 dr.
Sufficient aniline reel; Dissolve the resin in the ether, mix it with the collodion, and colour to taste. All that is necessary to apply the mixture is to dip the cork and the top of the bottle in it, turning it fbr an instant in the hand while the composition dries. The result is a semi-transparent varnish of pleasing appearance, especially if the cork of the bottle is previously sealed on top with sealing-wax.
(7) By heating milk with a little tartaric acid, the casein is coagulated. This casein is then treated with a solution containing six parts of borax to one hundred parts of water and warmed. It speedily dissolves and forms a very tenacious, durable, and inexpensive adhesive medium.
(9) 16 oz. rosin, 8 oz. sulphur; melt, and when cool reduce to powder. Mix with this some fine sand or brick dust, and use as stated. (10) Take a portion of a quill, put it into the handle, warm the tang, and insert it into the quill in the handle and press it firmly. This is a simple method, and answers the purpose required very well.
(10) Best isinglass, 1 oz., strong acetic acid, 3 oz.; put in a glass bottle, and dissolve by standing in hot water. Will join glass, china, etc, etc. Make the edges of the pieces to be joined hot, and apply the fluid cement. When cold this cement is solid; it must be made hot for use. (11) Equal parts of wheat-flour, finely-powdered glass, and chalk; add half as much brickdust, scraped lint, and white of eggs; mix to a proper consistency with water. This will resist heat. (12) To 1/2-pint of milk put a sufficient quantity of vinegar to curdle it, separate the curd from the whey, and mix the whey with the whites of four eggs, shaking the whole well to-gether. When mixed, add a little quicklime, through a sieve, until it acquires the consistency of a paste. This cement dries quickly, and resists the action of fire and water.
(11) One of the best cements for uniting glass to other substances is prepared by putting the very best and purest gum arabic into a small quantity of water, and leaving it till next day, when it should be of the consistence of treacle. Calomel (mercurous chloride er sub-chloride of mercury) is then added in a suitable quantity, enough to make a sticky mass, being well mixed on a glass plate with a spatula. No more is to be made than that required for immediate use. The cement hardens in a few hours, but it is wiser to leave it to itself for a day or two. To ensure success it is necessary to use only the best gum; inferior sorts are absolutely useless. (12) Wieder-hold recommends a fusible metal, composed of 4 parts lead, 2 parts tin, and 2 1/2 parts bismuth, which melts at 212° Fahr. The melted metal is poured into-the capsule, the glass pressed into it, and then allowed to cool slowly in a warm place. (13) Cailletet describes a process of soldering glass and porcelain to metal. The glass tube to be soldered is first covered with a thin coating of platinum or silver, by treating it with a film of platinum chloride or silver nitrate, and heating to dull red.
A ring of copper is next electro-deposited on the platinised tube, which can then be soldered like any ordinary metallic tube. Solderings effected in this manner are said to be very strong. The top of a tube attached to Cailletet's apparatus for liquefying gases terminates in a soldered end and successfully resists pressure over 300 atmospheres.
Dry. (a) Dry pocket glue is made from 12 parts of glue and 5 parts of sugar. The glue is boiled until entirely dissolved, the sugar is dissolved in the hot glue, and the mass is evaporated until it hardens on cooling. The hard substance dissolves rapidly in lukewarm water, and is an excellent glue for use on paper. (6) Take \ lb. of very best Scotch glue, melt it in a clean glue pot. When quite dissolved, pour off the clear part into another glue pot, add 1/2 pint boiling water, well mix. Then add 2 oz. best moist sugar; well mix the whole together, at the -same time keeping it quite hot. It may then be cast into moulds, or poured gently on a marble, or stone, or- slab. When nearly set, cut into strips for use. It is ready for use by moistening the strips with the tongue. It should be kept in boxes with a little powdered sugar or starch. This glue will be found both cheap and effective. It is much stronger than paste or gum.