SCIENCE— ADVERTISEMENTS 



\yfORE THAN ONE HUNDRED 



scientific laboratories are using the Type 

 K Potentiometer method for measuring hydro- 

 gen-ion concentrations. We have yet to learn 

 of a single case where, with proper manipu- 

 lation, a Type K Outfit has not unfailingly 

 given as highly accurate results as the ex- 

 perimental conditions permitted. 



TF YOU WANT FURTHER PROOF 



of the excellence of the Type K Potenti- 

 ometer as applied to hydrogen-ion measure- 

 ments, you will find them in Catalogue S75, 

 which also contains much valuable informa- 

 tion about such measurements. 



Leeds & Northrup Company 



Electrtcal Measuring Instruments 

 4901 Stenton Ave. Philadelphia, Pa. 



