7 6 DIRECTIONS tfOlt PERFORMING 



water will absorb the red vapor. This process can be re- 

 peated several times with the remaining gas. 



4O. I. The finely-powdered sal-ammoniac and lime may 

 be mixed in an evaporating-dish. The escaping ammonia 

 should be tested with a glass rod or tube wet with hydrochloric 

 acid. 



2. Heat a little aqua ammonia in the Florence flask. Col- 

 lect the vapor in an inverted bottle, to which is fitted a cork 

 and tube, with the inner extremity drawn to a fine point over 

 the spirit-lamp. Insert the cork, and then plunge the bottle 

 into a vessel of water. The water which passes in first will 

 absorb the gas so quickly as to make a partial vacuum, into 

 which the water will rush so violently as to produce a minia- 

 ture fountain. 



42. i. In making H, the directions given on pages 236-7 

 should be carefully observed. For purifying the gas a solu- 

 tion of potash should be placed in the flask d (page 42). If a 

 junk bottle be used the acid should be added slowly, as the 

 heat generated is liable to break the bottle. Pour the water 

 into the flask a until the lower end of the funnel is covered, 

 before adding the acid. The flow of gas may be regulated 

 by additions of acid, as may be wanted. One part of acid to 

 ten or twelve of water will liberate the gas very rapidly. If 

 it comes off very fast, the liquid is liable to froth over. The 

 philosopher's lamp, page 237, is very interesting. The jet 

 may be a straight glass tube drawn to a fine point over the 

 spirit-lamp. Large glass tubes or the beaks of broken re- 

 torts, held over this flame, will produce the singing tones, 

 though not as well as the apparatus figured in the book. The 

 tone may be regulated by the size of the flame, z. <?. the rapid- 

 ity with which the gas comes off, the size of the jet as well a a 

 the length and size of the tubes. The H can be collected 

 over the pneumatic cistern, or, since it is lighter than air, in 

 inverted bottles. As soon as the bottles are turned right side 

 up the gas will escape. To measure the H and O for the 

 " mixed gases," a receiver, with a stop-cock on top, which 

 may be connected by rubber tubing with the gas-bag, is very 

 useful. The oxygen may be passed directly into the gas-bag, 

 however, as on page 234, until it is about one-third full, when 



