14 INFLUENCE OF ENVIRONMENT ON SWEET CORN. 



METHODS OF ANALYSIS. 



Owing to the location of some of the cooperating stations, from 

 twenty-four to thirty-six hours would elapse between the time the 

 samples Were picked and their arrival at the Bureau; and if they 

 came in the afternoon, sixteen hours more would elapse before work 

 on them could be begun. The decrease in the sugar content in 

 transition from the field to the laboratory, as shown by the work 

 just reviewed, would, of course, give misleading results and defeat 

 the object of the investigation; therefore another plan had to be 

 devised. The most feasible one seemed to be to have the chemist 

 visit each laboratory at the time the corn was ready for harvesting 

 and make the analyses there. Accordingly analytical work was 

 begun at the South Carolina station about July 10, 1905. 



The sugar determinations were all made by reduction of alkaline 

 copper sulphate weighed as copper suboxid and calculated from this 

 to sugars by means of the Munson- Walker tables. To this end, 

 enough Fehling solution, as modified by Soxhlet, was made to com- 

 plete the determinations at all of the stations, and this, together with 

 the graduated glassware and weights, was sent to the various stations 

 in order to insure uniformity. 



The method employed was one devised at the Maryland experiment 

 station for use on dried corn and was found to be satisfactory for 

 green sweet corn. In brief it was as follows: 



Remove a sample of the corn, equal to about three rows of kernels, 

 pass through a food cutter, then pound in a mortar to break up the 

 germs. Wash 16 grams of this macerated sample into a 200-cc 

 flask with a 40-per cent boiling alcohol solution; place this on a hot 

 water bath and boil gently for one hour; cool, make up to mark with 

 95 per cent alcohol, shake thoroughly, and allow to settle. Draw 

 out 50 cc (4 grams of original sample) of the solution, add about 

 50 cc of water, and drive off the alcohol carefully. Wash the 

 dealcoholized solution into a 100-cc flask; add a sufficient quantity 

 of neutral lead acetate; 6 precipitate the lead with sodium carbonate: 

 make up to the mark with distilled water, shake, filter, and take 50 

 cc for inversion according to Clerget's method. The reduction was 

 then accomplished by means of the Soxhlet method as outlined in 

 Bulletin 107, Revised, of the Bureau of Chemistry, page 43, with the 

 exception that recently-boiled distilled water was not added at the 

 end of the reduction. 



U. S. Dept. Agr., Bureau of Chemistry, Bui. 107, Rev., p. 243. 

 6 In dry corn it is necessary to add alumina cream also. 



