﻿40 



THE AIR OF TOWNS. 



APPENDIX I . 



A RAPID METHOD FOR THE ESTIMATION OF CARBONIC ACID IN 



THE AIR. 



J=^ 



QTDa 



Fig. 1. 



(1) A standard solution of limeivater.— Fare water is left in contact with slack ad 

 lime until saturated. Tlie clear decanted liquid is diluted with ninety-nine tinies 

 its volume of distilled water. Make 1 quart or 1 liter. 



(2) Fhenolphthalein solution is made by dissolving one part of phenolphthalein in 

 five hundred times its weight of dilute alcohol [equal volumes of pure alcohol .'ind 



water]. Make 3 ounces or 100 cubic centimeters. 



(3) A 20-ounce stoppered dottle with (preferably) a hollow stopper 

 marked to hold 3 drams or 10 cubic centimeters. 



A sample of air is taken by blowing air into the clean stoppered 

 bottle (fig. 1) with bellows. Six minims or one-third of a cubic cen- 

 timeter of the phenolphthalein solution is then added, and the meas- 

 ured volume of lime water is run into the hollow stopper. 

 The limewater is poured into the bottle, the stopper inserted, the time noted, and 

 the contents vigorously shaken. If the red color of the liquid disappears in three 

 minutes or less the atmosphere is unfit for respiration. 



The stock of limewater should be kept in a bottle (fig. 2) fur- 

 nished with a tap and coated within with a film of paraf&io, and 

 in the neck an open tube should be inserted containing pieces of 

 caustic soda or quicklime. The phenolphthalein solution is best 

 measured by means of a narrow glass tube passing through the 

 cork of the bottle upon which the measured volume is marked. 

 If the cork fits easily the liquid may be forced up exactly to the 

 mark by pushing in the cork. 



The following are estimations made in this manner compared with the results 

 obtained by Pettenkofer's method : 



Time. 



Per cent vol- 

 ume of car- 

 bonic acid. 



Minutes. 



1 



li 



0. 1618 



If 



.1379 



H 



.1279 



3i 



. 07716 



4i 



. 05142 



5 



.0464 



n 



.0351 



