JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. 11 May 19, 1921 No. 10 



CHEMISTRY. — Note on the ice crystals which form on hare soils and 

 on the stems of plants.'^ Victor Birckner, Bureau of Chemistry. 

 (Communicated by Edgar T. Wherry.) 



The formation in frosty weather of ice crystals on certain soils and 

 on the stems of certain plants early attracted the attention of scien- 

 tists. The literature- on these very fascinating phenomena dates back 

 about a century and contains many speculations as to the cause and 

 the mode of formation of these structures. The explanations usually 

 offered rest almost entirely upon physical grounds, it being assumed 

 that the ice in question consists of pure frozen water. My own find- 

 ings have shown that ice structures both from bare soil and from the 

 stems of dittany {Cunila origan oides) contain organic material. 



A quantity of ice crystals from bare soil was taken to the laboratory 

 in a small tin pail. The well-known ice structures from Cunila stems 

 were also gathered, practically free from dirt, in a glass vessel and 

 taken to the laboratory. Both kinds of ice, after melting and filter- 

 ing, yielded a colorless opaque solution. After evaporation of 100 

 cc. of each solution in a platinum dish, the residue was weighed and 

 then ignited. From 100 cc. of filtrate from soil ice, 0.0032 gram of 

 residue was obtained, yielding 0.0016 gram of ash. The same quantity 

 of Cunila ice gave 0.0032 gram of residue, but only 0.0006 gram ash. 

 While, therefore, the two filtrates contained the same amounts of 

 stable solids, the proportion of the ash was much greater, and the 

 amount of organic matter correspondingly smaller, in the case of the 

 soil ice than in the ice from dittany. This may well be due to the 

 fact that the Cunila ice can be collected without difficulty in a state 

 of very high purity. 



Some of the earlier observ^ers of the ice formation on Cunila have, 

 it is true, suspected the presence of a foreign substance in these struc- 

 tures. In their papers they state that they have tasted the ice, but, 



1 Received February 10, 1921. 



^ Among the most important references to this subject are the following: W. W. 

 CoBLENTz, Jouru. Franklin Inst. 178: 589. 1914; Monthly Weather Review 42: 490. 

 1914; Scientific Monthly 2: 334. 1916. J. Sachs, Lehrb. Bot. (4th Ed.), 703. 1872. 



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