8o DIRECTIONS FOR PERFORMING 



enough water to reduce the mixture to a thin liquid. Shake 

 the flask until the whole interior is moistened. Insert the cork 

 and delivery-tube ; the middle bottle shown in the figure is not 

 necessary. Fill the pneumatic cistern with warm water, using 

 just as small a quantity as possible, since water absorbs the gas. 

 Pour in an ounce of the oil of vitriol through the funnel-tube, or 

 directly at the nozzle, by removing the ground stooper, if a 

 kind of flask be used which has one. The gas will come ofi 

 at once, even before the heat is applied. Collect the gas in 

 bottles and use directly, if convenient, otherwise put corks in 

 them and rub the nozzles well with tallow. Pass the gas 

 through cold water, as shown on page 88, or more simply, 

 through a tumbler of water. This will form chlorine water, 

 which should be bottled and kept in a dark place. 



2. Fill a test-tube nearly full of pure rain or snow watei, 

 and let fall into it a drop or two of the nitrate of silver solu- 

 tion. A drop of HC1 will form a cloudy white precipitate. 



91. i. Place on a clean white dish a few scales of iodine 

 and a bit of phosphorus as large as a pea. It will soon ignite. 



2. Fill three test-tubes nearly full of soft water. Pour in 

 one a few drops of a solution of bichloride of mercury, into 

 the second of sugar of lead, into the third of subnitrate of 

 mercury (formed by pouring NO 6 on mercury). Add to each 

 of these a few drops of the solution of iodide of potassium. 

 The first especially will produce a brilliant color (iodide of 

 mercury) ; the rapid change from yellow to red is very marked. 

 On continuing to add the iodide of potassium, the red precip- 

 itate will be dissolved and disappear. 



3. Make an additional quantity of the iodide of mercury, 

 as in the 2d exp. Let it settle. Pour off the liquid, and 

 then spread the sediment on a piece of heavy card-board, 

 making a red spot as large as a silver dollar. Dry it care- 

 fully. Then heat very strongly, when it will turn yellow. 

 Rub over the yellow spot the point of a knife several times, 

 bearing on very firmly, and a red mark can be seen. Lay away 

 the paper for a day or two, and the red color will spread ovei 

 the whole spot. 



4. Dissolve a few scales of iodine in fifteen or twenty times 

 its bulk of alcohol. Pour a few drops of this solution on a 



