t 8n ] 



out into a weighed crucible, the filter-paper burnt white, 

 rolled up in a platinum wire coil, and the ash added to the 

 precipitate. The crucible is to be placed on a piece of 

 black glazed paper, while the precipitate and the paper 

 ash are being put into it. The crucible is then to be placed 

 on a Bunsen flame or spirit lamp and the substance thoroughly 

 ignited. If any fragments spurt out, they will be noticed 

 on the black glazed paper and they can be put back into 

 the crucible. The crucible should then be left inside a 

 desiccator for over ten minutes and then weighed. The 

 precipitate in the three beakers is treated exactly in the 

 same way, the estimation of the strength of the sulphuric 

 acid being made in triplicate to ensure accuracy. 



1.394. The addition of Barium chloride in the pre- 

 sence of Hydrochloric acid results in the whole of the 

 Sulphuric acid in the beaker splitting up into BaSO 4 and 

 HC1. BaSO 4 is nearly insoluble in water, but in dilute 

 acid it is altogether insoluble. Hence the addition of a 

 few drops of HCl. 



1.395. The weight of the BaSO 4 being ascertained the 

 weight of pure H 2 SO 4 can be easily deduced. 



1.396. Suppose the weight of the crucible + precipitate 

 + ash of the filter-paper=3i < 92i grammes, and the weight 

 of the crucible alone = 29*336 grammes, and the weight of 

 the BaSo 4 precipitate and ash of paper = 2*585. A deduction 

 of 002 is usually made on account of the ash of the paper, 

 but this point may be separately determined by actual weigh-, 

 ment of the ash from a piece of filter-paper of the size and 

 quality used. The remainder, 2 583 grammes, is the weight of 

 the precipitate. The weight of the precipitate of all the three 

 beakers being thus ascertained, the average of the three 

 weights is taken. If the weights come to 2*583, 2-584 and 



2*583 + 2-584 +2*6 



2*6 grammes respectively, the average is - 



J 



2*589 grammes. 



