12 SODA ASH. 



following details of the most approved method of ascertaining the 

 amount of available alkali in any sample of soda ash, will best illustrate 

 the subject of alkalimetry. 



Some ordinary commercial oil of vitriol, which has usually tiie specific 

 gravity of 1845, water being 1000, is diluted with eight times its bulk of 

 distilled water — if distilled water be difficult to procure, clean 

 rain water will answer. This diluted acid is now tested as 

 to its strength, in the following way. A graduated glass 

 measure, is filled to a point between the division 23 and 24. It 

 is understood of course, that these numbers count from the zero 

 or 0°. the measure is now filled to zero with pure water, covered with 

 the hand, and inverted several times, so as to cause thorough mixture. 

 The diluted acid in every division of the measure ought to neutralise or 

 saturate one grain of pure or uncombined soda. To determine if this 

 is really the case, 100 grains of carbonate of soda, is obtained by heating 

 red hot for some time the common bicarbonate of soda, the heating con- 

 verts it into carbonate of soda, and 100 grains of this is now dissolved 

 in 3 or 4 fluid ounces of water in a Florence flask, and when the solution 

 has been effected it is filtered if- necessary. The filtered solution is now 

 coloured with some infusion of litmus and heated to near boiling. The 

 acid contents of the measure are now added little by little, each addition 

 is followed by brisk effervescence and a partial reddening of the litmus 

 colour, but on again applying heat, so as to boil the solution, this redden- 

 ing is changed back again to blue, and so with each addition of the acid, 

 until 58'5 measures have been added, when a reddening is produced 

 which boiling fails to restore to blue. This indicates that the soda of 

 the 100 grains of heated bicarbonate is neutralised or saturated. If the 

 58-5 measures of acid has exactly neutralised the 100 grains of pure 

 carbonate of soda, then the remainder of the diluted oil of vitriol may 

 be put in a stoppered bottle, and kept as a store of standard acid, to be 

 used for testing in the above way any sample of soda ash. If, however, 

 the diluted acid should be so strong that 50 measures of it effected satu- 

 ration of the above amount of carbonate of soda, then it is clear that 

 these 50 measures should have occupied the bulk of 58-5. A change in 

 accordance with that can easily be effected by adding to every 50 measures 

 of the acid in the measure, 8 5 of pure water, or to every 100 of the 

 acid 17 measures of water. If, on the other hand, more than 58-5 

 measures of dilated acid be recpiired, this indicates that the standard 

 acid is too weak to bring up its strength, there is no more convenient 

 method than to add of vitriol drop by drop, to the quantity of acid first 

 diluted, and subsecmently trying it with fresh carbonate of soda. 



With ordinary discrimination, one or two such trials is usually suffi- 

 cient to restore the acid to its proper strength. When this has been 

 done, the whole of the diluted acid should now be put aside as before, 

 with a label attached, to the effect that the alkalimeter, or graduated 

 measure, when filled to 23-5 with this acid, and then to 0° with water, 



