The Acidimetry of Hydrogen Fluoride. 



By 

 Tamemasa Haga, F.C.S., Rigakuhakushi, Asst. Prof. 



and 



Yükichi Osaka, Rigakushi, 



Imperial University. 



So far as we can find out, the acidimetry oï hydrogen fluoride 

 has not yet been particularly investigated. But it is well known that 

 as an acid it stands apart from hydrogen chloride and other strong 

 mineral acids. For while it even surpasses sulphuric acid in the 

 intensity of its reaction with water and many organic substances, it 

 yet shows such mild acidic characters, that its 'avidity' number places 

 it in this relation amonof veg-etable acids. Further, it not only decom- 

 poses the oxides oï some metalloids, such as boron, silicon, phosphorus, 

 and sulphur, forming fluorides possessing some degree of stability in 

 presence of water, but also gives with potash, soda, and ammonia, 

 salts which are alkaline to htnius. 



To investigate tlie subject we have experimented with the follow- 

 ing common indicators of neutralisation of acids by bases : litmus, 

 iacmoid, methyl orange, j)henacetolin, Phenolphthalein, rosolic acid, 

 cochineal, brazil wood, and turmeric paper. These indicators have been 

 prepared and used in the usual way, for the most part as described 

 in ISutton's Volumetnc Änaljisis. In order to ascertain what personal 

 difference there might be in the estimation of the particular shades of 

 colour which indicated neutralisation we wf)rked separately, and upon 



