BAIRD &TXTLOCK. (LONDON) LTD. 



DESCRIPTION OF FRIEDRICH'S PUMP (No. 3577), page 672. 

 (Translated from Annalen der Physik und Chemie, Neue Folgo, Band xxix., i886 v 



There are at present three different systems of mercury air pumps in use, viz., the Gcisslor's, the Toopler's, 

 and the Sprengel's. All have their advantages and disadvantages. The inconveniences are, for example, with 

 the Geissler's pump, the many stopcocks necessary ; with the Toepler's, the fragility of the many-branched tube 

 system ; while tlio Sprengel's pump is only useful for certain work. 



This mercury pump does not claim to remove every possible disadvantage that a mercury air-pump can 

 exhibit, and yet combine in itself all the advantages ; it is only intended to be an easily managed and handy 

 pump, which can be used for all kinds of work, and by which the production of a good vacuum is facilitated. 

 Ibis ;iir-pump shows a very peculiarly constructed principal stopcock. It is a three-way stopcock, but very 

 liiii rent from those of the Geissler's pump. The new three-way stopcock has two borings, which lie oblique to 

 the axis of the stopper. Each time the stopcock is turned, it opens or closes one or the other passage. The 

 advantages of these stopcocks are 



1. The removal of the tiresome furrow formation between collar and stopper in the periphery direction ol 

 the boring, whereby the stopcock easily becomes leaky. 



2. In place of the turning, in the Geissler's pump, of 45 to close the principal stopcock, such to be done by a 



turning of 90 and 180, which also contributes to the security of the work. 



Further, the few ground pieces are protected by mercury cups, in order that any casual entrance of air 

 may be guarded against. 



The Working of the Pump is very simple, as only one stopcock is used. With the rising of the mercury 

 the stopcock is so placed that the mercury in the widened reservoir A covers the stopcock. The purpose of 

 this is to be able to tako up a certain quantity of mercury without any escaping. The stopcock is then closed 

 jy turning it 90. When, by the sinking of the level in the mercury reservoir, the mercury has run out of the 

 :>ulb, the stopcock is further turned 90 in order to restore connection with the suction tube B. Whenever this 

 tappcns the stopcock is again shut, the mercury compelled to rise, and then the air through the stopcock driven 

 iut, and so on. Should, as by the analyses of the gases of the blood, moist gas be drawn out of the receiver, it 

 s only necessary to use a simple drying apparatus filled with chloride of calcium or other moisture-absorbing 

 naterial. The mercury air-pump can be made to any size, and with or without raising and lowering arrangement. 



In the fitting up and using the pump, the following practical suggestions may be found of use : 



The connections to be made with indiarubber tubing tied firmly with soft iron wire. 



DRYING APPARATUS. A small quantity of phosphoric anhydride to be placed in bulb C, and the narrow part 

 above it (D) to be filled with glass wool to prevent the phosphoric anhydride being drawn into the pump. Alter 

 this the mouth of the drying apparatus must be carefully cleansed and greased before the manometer is inserted. 



The mercury to be used must be pure and dry. Should the pump not act well at first it will be owing to 

 moisture in the tubes, which will be driven off by degrees and absorbed by the anhydrous phosphoric acid. The 

 mercury vessel must always be lifted slowly, otherwise there is a danger of the mercury falling against the stopcock 

 and breaking the pump. The gradual raising of the mercury facilitates also the better working of the pump. 



The glass tube of the drying apparatus must be connected with the funnel of the pump by means of a soft 

 indiarubber stopper or piece of tubing, and closed by mercury. This is as good as if the parts were ground to 

 fit, and the elasticity prevents breakage. 



If a high vacuum is required, the vessel to be exhausted should be allowed to remain on the pump for some 

 hours, and slightly warmed by means of a spirit-lamp. 



3581 



3582 



3581 Apparatus for the analysis of blood-gases, by Pfluger 



3582 Apparatus for the analysis of blood-gases, by Kronecker 



Nos. 3581 and 3582 can be fitted to No. 3578. 



4 10 

 4 10 



