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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.

      Pastes:

      Dextrine Pastes.—

I.—	Borax, powdered	60 parts
Dextrine, light yellow	480 parts
Glucose	50 parts
Water	420 parts

      By the aid of heat, dissolve the borax in the water and add the dextrine and glucose. Continue the heat, but do not let the mixture boil, and stir constantly until a homogeneous solution is obtained, from time to time renewing the water lost by evaporation with hot water. Finally, bring up to full weight (1,000 parts) by the addition of hot water, then strain through flannel. Prepared in this manner the paste remains bright and clear for a long time. It has extraordinary adhesive properties and dries very rapidly. If care is not taken to keep the cooking temperature below the boiling point of water, the paste is apt to become brown and to be very brittle on drying. {36}

      II.—Dissolve in hot water a sufficient quantity of dextrine to bring it to the consistency of honey. This forms a strong adhesive paste that will keep a long time unchanged, if the water is not allowed to evaporate. Sheets of paper may be prepared for extempore labels by coating one side with the paste and allowing it to dry; by slightly wetting the gummed side, the label will adhere to glass. This paste is very useful in the office or laboratory.

      III.—Pour over 1,000 parts of dextrine 450 parts of soft water and stir the mixture for 10 minutes. After the dextrine has absorbed the water, put the mixture over the fire, or, preferably, on a water bath, and heat, with lively stirring for 5 minutes, or until it forms a light milk-like liquid, on the surface of which little bubbles begin to form and the liquid is apparently beginning to boil. Do not allow it to come to a boil. Remove from the fire and set in a bucket of cold water to cool off. When cold add to every 1,000 parts of the solution 51 parts glycerine and as much salicylic acid as will stand on the tip of a knife blade. If the solution is too thick, thin it with water that has been boiled and cooled off again. Do not add any more glycerine or the solution will never set.

      IV.—Soften 175 parts of thick dextrine with cold water and 250 parts of boiling water added. Boil for 5 minutes and then add 30 parts of dilute acetic acid, 30 parts glycerine, and a drop or two of clove oil.

      V.—Powder coarsely 400 parts dextrine and dissolve in 600 parts of water. Add 20 parts glycerine and 10 parts glucose and heat to 90° C. (195° F.).

      VI.—Stir 400 parts of dextrine with water and thin the mass with 200 parts more water, 20 parts glucose, and 10 parts aluminum sulphate. Heat the whole to 90° C. (195° F.) in the water bath until the whole mass becomes clear and liquid.

      VII.—Warm 2 parts of dextrine, 5 parts of water, 1 part of acetic acid, 1 part of alcohol together, with occasional stirring until a complete solution is attained.

      VIII.—Dissolve by the aid of heat 100 parts of builders’ glue in 200 parts of water add 2 parts of bleached shellac dissolved previously in 50 parts of alcohol. Dissolve by the aid of heat 50 parts of dextrine in 50 parts of water, and mix the two solutions

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