CONTRIBUTIONS FROM THE FIRST CHEMICAL INSTITUTE OF THE 

 ROYAL FRIEDRICH-WILHELM UNIVERSITY OF BERLIN. 



THE TRANSITION TEMPERATURE OF MANGANOUS 



CHLORIDE: A NEW FIXED POINT 



IN THERMOMETRY. 



By Theodore W. Richards and Franz Wrede. 



Presented by T. W. Richards. Received October 7, 1907. 



In several previous articles one of us x has set forth in detail the 

 advantages of the transition temperatures of crystallized salts as fixed 

 points for thermometry. A number of suitable salts have been sug- 

 gested, and in particular the sulphate and bromide of sodium have 

 been carefully investigated. For these salts the transition tempera- 

 tures, referred to the international hydrogen scale, have been found to 

 be, respectively, 32.383°C. and 50.674°C. ; and both of these salts have 

 been shown to give points constant and definite enough for convenient 

 use for the above-mentioned purpose. 



Among the salts studied by Richards and Churchill in an approxi- 

 mate fashion was manganous chloride (MnCl 2 • 4H 2 0). This salt has 

 also been investigated roughly by Kuznetzoff, and by Dawson and 

 Williams. 2 All of these investigations were merely approximate ; no 

 attempt was made to correct the thermometer for the errors of ordinary 

 thermometry. Therefore they were none of them suitable for denning 

 the point with sufficient exactness for the present purpose. On the 

 other hand all of the investigators agreed in maintaining that the point 

 was constant and definite. Therefore it promises well ; and the pres- 



1 T. W. Richards, Am. J. Sci. [4], 6, 201 (1898) ; Richards and Churchill, These 



Proceedings, 34, 10 (1899) ; Richards and Wells, These Proceedings, 38, 431 (1902), 



fl^ 41, 435 (1906). These four papers are all to be found in full in the Zeitschr. 



O fur phys. Chem., the references being respectively 26, 690 (1898) ; 28,313 (1899) ; 



2? 43, 465 (1903) ; 56, 348 (1906). The present paper also will appear in German in 



I that periodical. 



IT 2 Kuznetzoff, Chem. Centralblatt, 1890, I, 24ft ; Dawson and Williams, Zeit. 

 * fur phys. Chem., 31, 59, 1899. 



