During the “Snow Cornice 1949” expedition of the Arctic Institute of North America to Alaska a day was spent testing the methods proposed by the writer for determining the liquid water content of snow. These appeared in the Schweizerische Mineralogische und Petrographische Mitteilungen (Vol. 28, 1948, p. 355–61) and received comment in the Journal of Glaciology, Vol. 1, No. 7, 1950, p, 359.
The methods consist in measuring the temperature depression produced by the addition of a weak solution to the wet snow or by titrating a portion of the diluted solution drawn after mixing with the snow. Sodium hydroxide was used because it has a constant temperature depression coefficient at convenient concentrations: 3.41 at 0.2 normal, and 3.40 at 0.5 normal.
A specially made mercury thermometer was used, graduated from +0.1° to −2° in 1/100 intervals. Titration was with hydrochloric acid and a phenolphthalein indicator. A cylindrical thermos flask of cm. internal diameter and 23 cm. deep was used.
The samples consisted of about 100 gm. wet snow to which was added 100 gm. of 0.5 normal sodium hydroxide, which had been cooled down to 0°. The solution was conveniently carried in 100 gm. portions in rubber-stoppered small pyrex bottles. It is, of course, not necessary to cool the solution, as it is easy to correct for its temperature.
When the solution was added to the snow, there was a rapid cooling and some of the snow formed hard lumps, in part adhering to the flask. The mixture was stirred with the thermometer until all the lumps had disintegrated. The thermometer initially read a few hundredths lower than the equilibrium temperature, which when reached, remained stable for one or two minutes. In order to obtain a mixture sufficiently fluid for easy stirring, it was necessary to mix approximately equal weights of snow and solution. After measurement of the temperature depression, 25 ml. of solution was poured off and titrated. Five samples of wet névé from a few inches below the surface were tested, the last one with water added.
The following formulae were used for computation:
x = gm. liquid water
t = temperature depression
b = gm. wet snow
c 0 = gm. solution added to snow
m 0 = titer of solution c 0
m 1 = titer of solution after mixing with snow
β = temperature depression coeficient of solution
In the first sample it was noticed that some snow was poured off with the solution to be titrated, which accounts for the large discrepancy. The other tests show fair agreement of the two methods. The accuracy of the thermometer was not tested.
Laboratory work is planned to clear up the problem of liquid water content determination by testing different methods on samples of known water content. It must here be mentioned that dielectric measurements done at the Central Sierra Snow Laboratory by Mr. B. Lyle Hansen (private communication) indicate that the energy of absorption of a water film on ice crystals may introduce an error into calorimetric determinations. This matter will also be investigated.
Henri Bader (Rutgers University, New Brunswick)
12 April 1950.