Asbestos board

The steam-distillation is continued for 5 minutes after steam can first be seen entering the condenser the ideal rate of distillation is about 4 -5 ml. of distillate per minute, but this is not critical and may be varied within reasonable limits. The receiver J is then lowered from the lip K of the condenser and the steam-distillation continued for a further two minutes, thus ensuring that no traces of liquid containing ammonia are left on the inside of the condenser. At the end of this time any liquid on the lip K is rinsed with distilled water into J, which is then ready for titration. It is important that the receiver and its contents are kept cold during the distillation and it is advisable to interpose a piece of asbestos board or other screen so that it is not exposed to the heat from the burner under the steam generator. 

Electric hot plates may also be employed for heating. These should be of substantial construction and be provided with three-way switches. The diameter of the heavy cast-iron top may vary between 5 and 10". It is usually advisable to interpose a sheet of asbestos board between the metal top and the vessel to be heated, particularly if the contents of the latter are liable to bump. ... 

Fig. 11,10, 3, depicts a housing for the apparatus of Fig. 11,10, 2, a it is easily constructed from lengths of angle iron and asbestos board. If desired, torch bulbs may be fixed in the appropriate holders in the walls, and connected with a dry battery or accumulator in order to provide illumination of the melting point apparatus. The electric bulb immediately behind the apparatus should be connected to an inde pendent micro-switch. Alternatively,... 

Several forms of apparatus employing electrical heati iig wi 11 be described. A simple form may be readily constructed from a domestic electric iron of 400-500 watts rating. The handle is removed, and two holes of 8 mm. diameter are drilled through the base (ca. 11 mm. thick) so that they meet in the centre of the block. One hole is for a 360° thermometer (small bulb) the other hole is spare and can be used for comparison with a standard thermometer. The heater is mounted on a sheet of thick asbestos board which is fixed to an appropriate wooden base. The wires from the heating unit are connected to two insulated terminals fitted on the board (Fig. 11, 11, 1). The rate of heating is controlled by either of the following methods ... 

An iron saucepan with a layer of sand at the bottom is quite satisfactory the distilling flask is immersed in the bath to within 2 cm. of the side arm, and two asbestos boards, cut to fit the neck of the flask, rest on top of the bath (as in Fig. II, 5, 3).. Somewhat better rosiilts are obtained if the bath is filled with nickel shot. 

Pa.ints, Paints (qv) prepared from poly(vinyl acetate) and its copolymers form flexible, durable films with good adhesion to clean surfaces, including wood, plaster, concrete, stone, brick, cinder blocks, asbestos board, asphalt, tar paper, wahboards, aluminum, and galvani2ed iron (147). Adherence is also good on painted surfaces if the surfaces are free from dirt, grease, and mst. Developments in emulsion polymeri2ation for paint latices have been reviewed (148). 

Asbest-aufschlkmmung, /. asbestos suspension -drahtnetz, n. asbestos wire gauze, -faser, /. asbestos fiber. -filz,m. asbestos felt. -flocken f.pl. asbestos flocks, asbestos wool, -gewebe, n. asbestos cloth, -handschuh, m. asbestos glove, -holz, n. asbestos lumber, -luftbad, n. asbestos air bath, -oUtb, n, short-fibered asbestos, -papier, n. asbestos paper, -pappe,/. asbestos board, -platte, /. asbestos plate or board, -schale, /. asbestos dish, -schicht, /. asbestos layer or bed. -schlefer, m. asbestos alate. -schirm, m. asbestos screen, -schnur, /, asbestos twine or cord, -schurz, m -schurze, /, asbestos apron. -woUe, /. asbestos wool. 

The boiler can be heated with an ordinary bunsen burner but its base should be coated with a in. layer of asbestos paste—this is absolutely necessary with soda glass. It may be desirable to employ an asbestos board G for deflecting radiant heat from the boiler, thereby protecting the ring seal and the waxed cork of the water jacket. 

If the flask is not protected with an asbestos board or the equivalent, decomposition occurs where the substance is superheated on the side walls of the flask. If crystals of the cyanide are allowed to remain on the upper walls of the flask, they are not easily washed down and so are not hydrolyzed. 

In a i-l. round-bottom flask are placed too g. of -nitrobenzyl cyanide. A solution of 300 cc. of concentrated sulfuric acid (sp. gr. 1.84) in 280 cc. of water is prepared, and two-thirds of this solution is poured on to the p-nitrobenzyl cyanide. The mixture is shaken well, until the solid is all moistened with the acid. Any solid material sticking to the walls of the vessel is now washed down into the liquid with the remainder of the acid, the flask is attached to a reflux condenser, then set, without shaking, over a 10-cm. hole in a large sheet of asbestos board which rests on a tripod, and heated until the mixture boils. The boiling is continued for fifteen minutes. 

Test No 2 A small sample of explosive is placed on an asbestos board and a small flame of a Bunsen burner is directed against it for 10 seconds. It is considered noninflammable if it does not ignite in this period. Control samples of known explosives should be included for comparison... 

Fill a small crucible (or a thimble) with the sample and by inverting transfer onto a piece of asbestos board... 

The appatatus consists of a brass cup (See Fig F10), supported by a metal heating plate, XA inch thick and 6 inches in diameter (not shown here). In the center of the plate there is a plane depression l/32 inch in depth, and of just sufficient diameter to fit the cup. There is also a circular opening 2-3/16 inches in diam, cut thru the plate, centering with the center of die above-mentioned depression. The plate is covered with a sheet of hard asbestos board % inch thick, and of die same shape as the metal plate and with a hole cut in the center just to fit the cup. Heat may be supplied from any convenient source. The use of gas burner, electric heater, or alcohol lamp Is permitted, but under no circumstances are... 

Now carefully heat the mercury to boiling and distill at a slow rate. It may be necessary to fashion a shield of asbestos paper over the top of the distilling flask to diminish the radiation and prevent the mercury vapor from condensing before it reaches the outlet tube. If the upper neck of the distilling flask tends to get hot, cut a round hole in a piece of asbestos board of such size as to make a tight fit over the neck of the flask and slip it over the neck for a shield, as shown at G. The mercury should come over perfectly clean. If it looks at all dim, it is probably because the air pressure in the flask has not been reduced low enough. 

Fill a small iron crucible about one-half to two-thirds full of magnesium powder. Bore a pinhole in the iron lid and then place the lid on the crucible. Lute the lid to the crucible with wet asbestos pulp and close the hole with the same material. (If a lid is not available, twist the crucible on a piece of asbestos board like a biscuit cutter until a deep groove has been cut in it and then lute it to the crucible as before.) Dry the crucible and its contents in an air oven or on the hot plate and when they are dry pierce a small hole in the asbestos plug with a pin. Place the crucible in a circular hole... 

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