222 S. L. Penfield and G. S. Jamieson — Tychite. 



Tychite, 2MgC0 3 . 2N"a a C0, . Na 2 S0 4 . 



Northupite, 2MgC0 3 . 2Na 2 C0 3 . 2NaCl. 

 Other physical properties are given below : 



Specific gravity. Index of refraction, n y . 



m , . 2*456 natural. 1*508 natural, 



lycnite, 2>58g artificiaL 1 . 510 artificial 



AT ,, .. 2*380 natural. * 1*514 natural. 



JNortnupite, a » hh .. a . , 

 r ' 2*377 artificial. 



Theoretical. — There seems to be far more interest connected 

 with the present investigation than the mere description of a 

 new species. Although northnpite is somewhat slowly soluble 

 in cold water, and is quickly decomposed by boiling water with 

 the separation of magnesium carbonate, tychite is almost 

 insoluble, even when its fine powder is treated with boiling 

 water. ITnlike most insoluble substances, however, which 

 precipitate quickly as soon as the constituents necessary for 

 their formation are brought together, northupite and tychite 

 are formed slowly. In de Schulten's experiment, northupite 

 was obtained after seven hours heating, and in ours it took 

 nearly as many days of continued heating to obtain crystals of 

 tychite. It would seem as though the slowness with which 

 these substances are formed might be taken as an indication of 

 their having a complex molecular structure, and that the 

 element of time is necessary for the arrangement of the atoms 

 in a state of equilibrium. Just what the arrangement of the 

 atoms is, we are not able to determine, but the simplest and 

 most symmetrically developed formulas which suggest them- 

 selves are the following : 



Na-(K^O-Na 



^o -• - O^ 



Northupite, Na-O-tCo-Mg-Cl Cl-Mg-O^C-O-Na 



\o - C - o^ 



Na-(X>0-Na 



Na-(K^O-Na 

 n - C - Q^ 



Tychite, Na-O-C-O-Mg- (S0 4 ) - Mg-O-C-O-Na 



\o - c - o^ 



Na-CV^O-Na 



In these formulas the four carbon atoms are united by 

 oxygen in ring formation, which it may be assumed it takes 

 some time to establish, but, when once established, accounts 



