72 DIRECTIONS FOR PERFORMING 



prevent any running over upon the table. Neatness in ex- 

 periments is essential to perfection, and often to success. 



15. i. The cabbage solution is made by steeping p.urple cab- 

 bage leaves in water. A little lemon-juice or vinegar will turn 

 it to a bright red, and a little of the potash solution to a deep 

 green. Add a little alcohol to the red solution, to keep it 

 from freezing, and bottle it for use. Dissolve a little of the 

 dry litmus in water, filter and bottle it. These are to be used 

 in testing the alkalies and acids. Dissolve also a stick of the 

 potash in water, filter and bottle. Fill two test-tubes nearly 

 full of water ; color one with the cabbage and the other with 

 the litmus solution. Add a few drops of the potash solution 

 and of the sulphuric acid alternately to each. The color can 

 be changed at pleasure. 



Take a small bit of tubing, and heating the ends in the 

 flame of the spirit-lamp (the greatest heat is near the tip of 

 the flame), seal up the opening. This will be useful to dip 

 into the acid or alkali, as it will remove a drop more readily 

 than by dropping from the bottle. 



2O. Pulverize an ounce of the potassic chlorate very care- 

 fully; stir in it one-fourth of its weight of the black oxyd of 

 manganese and place the mixture in the copper retort, at- 

 tach the tubing and gas-bag as shown in the figure of p. 

 234 ; or in the Florence flask, attaching a delivery tube, as 

 shown in figure on p. 20. The glass tubing may be heated 

 in the flame of the alcohol-lamp and bent to the desired 

 shape, or it can be broken into short lengths by simply start- 

 ing the break in the tube by a mere scratch with a three-cor- 

 nered file and then connecting the pieces of glass tubing with 

 a short bit of the small rubber tubing, as in the figure on 

 p. 20. The gas may be passed off from the gas-bag, or di- 

 rectly from the retort into the pneumatic cistern, C, across 

 which is placed a jhelf perforated, to permit the gas to bubble 

 up into the receiver, J. The pneumatic cistern may consist 

 of a tub of water. The bottles for collecting the gas are sunk 

 into the water until filled, inverted, and then lifted up on 

 the shelf, carefully keeping the lower edge of the bottle be- 

 neath the water. A large tin pan, without any shelf, may be 

 used as a cistern by filling the bottles full of water in a deep 



