224 BALLOONS. 



pipe into some soap-water contained in a saucer, take it out ag 

 and turn the gas on. The liquid film which has formed across t 

 mouth is blown out by the gas into a bubble ; when the mouth i 

 turned upwards, and the bubble has a diameter of from 8 to 15 

 it rapidly rises to the ceiling by virtue of its lightness. 



If coal-gas cannot be obtained, hydrogen must be m 

 Hydrogen is one of the constituents of water, and may be prepared 

 bringing water in contact with zinc and sulphuric acid. The zinc 

 used in small pieces, such as may be obtained by * granulating ' it 

 the manner described at page 27, or zinc-clippings may be purch 

 of a tin-smith and cut up into small pieces. The sulphuric acid 

 must be diluted before it is poured over the zinc. If sulphuric acid 

 is poured into water, considerable heat is evolved ; but this heat i 

 much greater when the water is poured into the sulphuric aci 

 To avoid accidents in consequence of the breaking of the vesse' 

 containing the mixture, or the splashing about of the acid, the 

 mixture is best made in the following manner. Pour about 500 CC 

 water into a vessel of 1 litre capacity, such as a large stoneware 

 pickle jar, which is placed in a bowl (an earthenware or china 

 washhand-basin) partly filled with water ; the water somewhat 

 cools the jar and prevents the escape of the acid in case the jar 

 should break ; now pour 50 CC sulphuric acid in a small stream into 

 the water, stirring the water continuously with a glass rod. 

 the jar remain in the bowl until it is entirely cold, and then trausfi 

 the dilute acid into a bottle. Like hydrochloric acid, dilute 

 phuric acid produces spots upon articles of clothing ; care shou 

 therefore be taken in handling it, and spots should immediately 

 touched with a solution of ammonia carbonate. The concentra 

 acid has a most destructive action upon textures, and most vegeta 1 

 and animal substances, which are rapidly decomposed and charred 

 by it. When a drop of it falls upon anything, it should first he 

 wiped off' with a piece of dry blotting-paper or an old rag, which 

 should be kept ready for such an emergency ; the place should then 

 be immediately washed with a great quantity of water, and final! 

 moistened with ammonia carbonate ; but the appearance of a 

 can never be entirely prevented. 



For the reception of the gas which is generated with effervesce; 

 when dilute sulphuric acid is poured over zinc, an apparatus is 

 required of which fig. 154 represents one of the simplest forms. A 

 bottle with a wide neck is provided with a twice perforated cork ; 

 through one hole passes the tube-funnel t, which reaches nearly 

 to the bottom of the bottle ; through the other hole passes a tube 

 bent twice at right angles, one branch of which passes through 



