C 68 3 



A. a. Upon placing a bit of reddened litmus 

 paper in water containing it, the red colour will 

 gradually difappear and the blue return ; but if 

 a portion of the water be firft evaporated, it will 

 become turbid, the fuperabundant fixed air, which 

 keeps the chalk in folution, will fly off, and the 

 chalk be depofited : now place the litmus paper in 

 it, and no alteration of colour will take place. 

 The calcareous earth not being in fuffkient quan- 

 tity in the water to combine with the vinegar, that 

 gives this red colour to the litmus paper. 



b. Upon putting into it a piece of Brazil 

 wood paper, the red colour will be by degrees 

 changed to a violet ; but if a portion of the water 

 be evaporated, and the remainder be fuffered to 

 fettle as above, no alteration will happen, unlefs 

 the water contain alfo Gypfum, or fome alkali. 



c. On adding the acid of fugar to this water 

 a precipitate takes place, as defcribed (page 62. 

 b.) it combines with the calcareous earth, and 

 falls to the bottom, while the fixed air remains 

 diffolved in the water. 



d. A folution of foap being added to this 

 water, the fame appearances take place as de- 

 fcribed (page 56. e.) The lime and oil forming 

 an earthy foap, while the fixed air unites to the 

 alkali. 



B. e. The fixed air contained, if in any quan- 

 tity, may be difcovered by the method defcribed 

 (page 46. d. e.) or by adding a little vitriolic acid 

 to it before the diftillation. The vitriolic acid 

 unites with the lime, and forms Gypfum, which 

 remains diffolved in the water, while the fixed air 

 is detached. 



ALUM. 



