334 Journal of Agricultural Research voi. iii. no. 4 



temperature, which was maintained by the aid of artificial heat when 

 necessary. The remaining six crates of each variety were placed in a cold- 

 storage room, which was kept at a fairly uniform temperature of 4° C, 

 by means of circulating brine cooled by ice and salt. Thus, both the 

 lot stored at the usual storage temperature and that placed in cold storage 

 were submitted to the same preparatory curing process. In order to 

 determine the carbohydrate changes which occurred in these lots during 

 the season, samples were analyzed on the day the potatoes were dug 

 and at intervals of about a month during the course of the experiment, 

 from October to June. In these samples the water, starch, reducing 

 sugar, and total sugar were determined. 



EXPERIMENTAL METHODS 



Sampling. — For each set of determinations, a random sample of 4 to 

 5 kg. was taken. The roots were rapidly washed and wiped with a 

 towel. When the surface had become entirely dry the roots were cut 

 up as quickly as possible and ground in a power-driven meat grinder 

 having a face plate with holes 3.2 mm. in diameter. The operation of 

 cutting and grinding required about 10 minutes. The mash thus 

 obtained was thoroughly mixed on a glass plate and quartered twice. 

 The final sample thus obtained was placed in a crystallizing dish and 

 covered with a damp towel while the samples for sugar, starch, and 

 moisture determinations were being weighed out. 



Moisture. — For the determination of moisture, samples of approxi- 

 mately 10 gm. were transferred into tared weighing bottles and accu- 

 rately weighed. The material was covered with 95 per cent alcohol, 

 which was subsequently evaporated in vacuum desiccators containing 

 sulphuric acid. The samples were then dried to their lowest weight in a 

 current of hydrogen in a vacuum oven at 78° C. The drying required 

 15 to 18 hours, during which the bottles were weighed three or four 

 times. 



Starch. — It was not possible to make the starch determinations 

 immediately. Samples of 25 gm. correctly weighed to i cm. were there- 

 fore transferred to Erlenmeyer flasks of 200 or 250 c. c. capacity and 

 covered with 150 c. c. of 95 per cent alcohol. A little precipitated 

 calcium carbonate was added to the flasks, which were then brought to 

 the boiling point in a water bath. Subsequently the samples were 

 washed with alcohol into tared porcelain extraction thimbles, 75 mm. 

 high and 40 mm. in diameter, with perforated bottoms which were 

 covered with filter paper cut to fit. Another piece of filter paper was 

 pressed down upon the material and held in place by means of a cotton 

 plug. The thimbles were supported well up in Soxhlet extraction ap- 

 paratus and extracted with strong alcohol for 12 hours. After extrac- 

 tion the cotton and filter paper were removed, and the thimbles were 



