UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 895 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
PROFESSIONAL PAPER 
May 10, 1921 
THE FREEZING POINT OF POTATOES AS DETER- 
MINED BY THE THERMOELECTRIC METHOD. 1 
By R. C. Wright, Physiologist, Office of Horticultural and Pomological Investigations, 
and R. B. Harvey, Plant Physiologist, Office of Plant Physiological and Fermentation 
Investigations. 
CONTENTS. 
Historical summary 1 
Plan of this investigation 2 
Freezing points of different varieties and 
groups of potatoes 3 
Page, 
Undercooling •. 5 
Inoculation 6 
Summary -. 7 
HISTORICAL SUMMARY. 
Definite data on the exact freezing point of the potato {Solarium 
tuberosum) are not to be found in the literature, owing possibly to the 
wide variations in the methods and materials used by different in- 
vestigators. Up to the present time practically all data on the freezing 
point of potato tubers have be en obtained by the use of thermometers of 
the mercury or a similar type. So far as published data are concerned, 
Apelt 2 was apparently the first to use the thermoelectric method of 
determining the freezing points of potatoes. 
Muller-Thurgau 3 was one of the first investigators to publish the re- 
sults of investigations on the freezing point of potatoes. In 1880, in 
presenting his findings in connection with various plants, he gave 
the freezing point of potatoes as 30.21° F. (-1.8° C). Appleman 4 
in his study of the changes in potatoes during storage found that 
the tubers freeze when the temperature is between 28° and 26° F. 
(-2.2° and -3.3° C). According to the results of Jones, Miller,. 
1 This bulletin presents the results of a portion of the work carried on in the Bureau of Plant Industry 
under the project "Factors affecting the storage life of vegetables." 
8 Apelt, Arthur. " Neue Untersuchungen iiber den Kaltetod der Kartoflel." Beitrage zur Biologie 
der Pflanzen Cohn. Bd. 9, p. 215-261. 1907. 
3 Miiller, Hermann, Thurgau. TJeber das Gefrieren und Erfrieren der Pflanzen. In Landw. Jahrb. 
Bd. 9, p. 133-189, pi. 1-4. 1880. 
4 Appleman, C 0. Changes in Irish potatoes during storage. Md. Agr. Exp. Sta. Bui. 167, p. 327-334. 
1912. 
424°— 21— Bull. 895 
