268 Kreider and Breckenridge — Separation and Sodium^ etc. 



causing explosions which vary in force and seriousness accord- 

 ing to circumstances. 



We, therefore, selected a strong distilling flask of about 

 100 cm^ capacity and sealed into the tubulation a stoppered 

 funnel which reached well into the bulb. The stop-cock of 

 this funnel was carefully cleansed of vaseline and lubricated 

 with metaphosphoric acid obtained by boiling syrupy ortho- 

 phosphoric acid until the temperature of 350" C. had been 

 attained.* The side neck of the flask was inclined upward for 

 a short distance before being bent into the receiver, with which 

 it was connected by a rubber stopper through which the tube 

 extended for a safe distance. An ordinary bottle of 250 cm^ 

 capacity served for a receiver and was closed by a doubly per- 

 forated stopper. Through one of the perforations the adapter 

 from the condenser was entered ; through the other connection 

 was made with a small glass bulb inserted between the receiver 

 and the next tube, containing moistened sticks of caustic potash, 

 in order to prevent the potash from reaching the receiver in 

 case of an accident to the pump. The object of the potash 

 was to absorb any chlorine resulting from the inevitable slight 

 decomposition of the acid, and thus to protect the mercury of 

 the pump. For the exhaustion an automatic pump was 

 employed and generally twenty minutes would suffice to reduce 

 the pressure to about 8™°^, when the distillation was begun. 

 The pump gradually reduced the pressure, which was kept at 

 about 3 to 5™'\ The bottom of the distilling flask was covered 

 with a layer of fine porcelain chips to a depth of about 1 cm^ and 

 the whole flask was surrounded by a cylinder of thin sheet iron 

 closed below, while the upper opening was protected by an 

 albestos cover. By this means heat was uniformly applied to 

 every part of the flask and up to the point at which, if the acid 

 condensed, it would flow into the receiver. Three or i cm^ of the 

 acid were admitted to the flask, after which the temperature was 

 raised to about 130° C. and the acid admitted at about the same 

 rate that it dropped from the condenser, care being taken to 

 prevent the liquid in the distilling flask from disappearing 

 entirely. No danger was experienced in admitting the acid ; 

 the porcelain chips distribute the heat and prevent the colder 

 acid from reaching the glass. 



Careful compliance with the above conditions will secure 

 satisfactory results. As a rule we succeeded in distilling at the 

 rate of 25 cm^ to 40 cm^ per hour, and when it is remembered 

 that the product is the dihydrate of perchloric acid, the most 

 concentrated form in which it is stable, and of which 0*1 grm. 

 of potassium oxide requires only 0*16 cm^, it will be seen that 

 by this process the acid may be prepared without great difficulty. 



* This lubricant will be found entirely satisfactory and greatly preferable to 

 vaseline in roany other operations where the greasy effect of the latter is objec- 

 tionable. 



