BAIRD ^TXTLOCK (LONDON) LTD. 



Hold the bottle containing the sample in the left hand, and place it immediately under the end of the burette, 

 then add the soap solution, a few drops at a time, by cautiously opening the stopcock, taking care to exercise 

 no undue pressure as that is apt to cause the stopcock to jamb. After each addition, place the stopper in the 

 bottle, and shake vigorously. At first any lather produced will disappear rapidly, but towards the end of the 

 operation the lather will show a tendency to persist, and the bottle should then be placed on its side after each 

 shaking, to present as much surface as possible. The test is complete when this lather remains for five minutes 

 without breaking. During the test a guide to its progress may be gauged from the sound of the solution on 

 shaking. 



While the water is still hard, the sound is metallic, becoming less distinct on nearing the completion of the 

 test, and eventually giving place to a soft sound. 



When the test is completed, read off the number of cubic centimetres on the burette. This will give the 

 degrees of total hardness direct. Say, for example, that the burette showed four large divisions or cubic centi- 

 metres, and four small divisions or tenths of a cubic centimetre, then the reading would be 4.4 grains per gallon. 

 Should the sample use more than 7 cubic centimetres soap solution, take only 35 cubic centimetres, or half the 

 quantity, and dilute to the 70 cubic centimetres mark with the distilled water supplied. As distilled water itself 

 shows a reaction with soap solution, i cubic centimetre must be deducted from the test made with the diluted 

 sample. The result is then multiplied by two, as only half the quantity was taken. 



Example. 5 cubic centimetres soap solution used in testing diluted sample, distilled water (35 cubic centi- 

 metres) used I cubic centimetre soap, therefore 5 c.c.-i c.c. =4 c.c., 4 c.c. X2 c.c.=8 c.c. or eight degrees of total 

 hardness. 



To find the temporary hardness, i.e., the carbonates of lime and magnesia held in solution by carbonic acid, 

 the bottle labelled " Standard Acid A " is used. The estimation is conducted as follows : By means of the 100 

 cubic centimetres measure take 70 cubic centimetres of the sample and transfer to the porcelain basin, then fill the 

 other 25 cubic centimetres burette with the acid A, and adjust to the zero mark as before. Add two drops of 

 the methyl orange solution to the sample in the porcelain basin, and stir cautiously by means of the stirring rod 

 until the solution is uniformly coloured. Then add the acid solution from the burette, a few drops at a time, and 

 stirring after each addition until the colour changes to a faint pink. At this point the carbonates have been 

 neutralised by the acid, and the reading on the burette will represent the temporary hardness of the sample. 



Example. Total hardness found by soap solution 8 cubic centimetres, temporary hardness found by acid 

 A=4.i cubic centimetres. Therefore 8-4.1=3.9, a figure which represents the permanent hardness of the water 

 in grains per gallon, or the salts of lime and magnesia other than carbonates in solution. 



2. Strength ot Lime Water by means of Standard Add B. 



Titrate 35 cubic centimetres of the lime water with Standard Acid B, as in estimating temporary hardness. 

 To produce a pink colour with methyl orange, 16.2 cubic centimetres should be required. 



3. Silver Nitrate Solution for testing if correct quantity ot lime has been added. 



Place a little of the sample of water in a test tube and add a few drops of the silver nitrate solution. If the 

 solution turns brown, excess of lime has been added ; if the colour is milky white, insufficient lime is present ; 

 but if only a pale yellow colour is apparent, then the correct proportion of lime has been introduced. 



5065 



5065 Dr. Adeney's Apparatus for observing the rate of absorption of oxygen by polluted water 

 and other fermenting liquids. Price complete with I.R. blower in polished mahogany 

 case 



It is now agreed that the quality of a sewage effluent can best be ascertained by determining the rate at which 

 it takes up dissolved atmospheric oxygen, after the suspended matters have been removed, and this apparatus 

 has been designed for the purpose. Its form will be understood from the above sketch, full descriptive circular 

 on application and with each instrument. 



1 10 



CROSS STREET HATTOTST GARDETST, E-C 



928 



