16 BULLETIN 859, U. S. DEPARTMENT OF AGRICULTURE. 



250 cubic-centimeter tared beaker and dried at 60° to 70° C. to 

 apparent dryness, after which, it was dried in vacuo at 80° C. until 

 the loss between two successive weighings was negligible. For ash 

 the residue was ground in a mortar, then placed in the vacuum oven 

 over night and approximately one-half of the total sample used for 

 the crude-ash determination. 



Acidity. — All acid determinations were made with fresh material. 

 Two hundred grams of tomatoes wer,e pulped and placed in a liter 

 volumetric flask, made up to volume with cold distilled water, and 

 toluol was added to prevent the growth of organisms. After stand- 

 ing three days, 50 c. c. aliquots were titrated against approximately 

 a tenth normal sodium-hydroxid solution (N/10 NaOH), using 

 phenolphthalein as the indicator. No trouble was experienced in 

 determining the end point. Separate determinations were made 

 until the duplicateschecked. In order to determine the effect of enzyms 

 on acid content, a sample treated with boiling water was titrated 

 three days later and the results compared with one using cold 

 water. For the former, 200 grams of material required 14.28 c. c. 

 N/10 NaOH, and for' the same quantity of material employing cold 

 water, 14.18 c. c. N/10 NaOH were required for neutralization. 



Free reducing substances. — One- tenth of the original alcoholic extract 

 was evaporated nearly to dryness while the same part of the residue 

 was being extracted on a filter paper with warm water (35° C). 

 Very little reducing substance remained after extracting the original 

 residue with alcohol, as described under "Sampling and preserva- 

 tion," but the warm-water extraction was performed to insure the 

 removal of final traces. The aqueous extract was combined with the 

 residue from the alcoholic portion and filtered into a 250 c. c. volu- 

 metric flask, after which the filter paper was thoroughly washed. 

 One cubic centimeter of lead-acetate solution (a saturated solution 

 of the normal salt) was added and the solution made up to volume 

 at 20° C. The whole was filtered immediately and the excess of 

 lead removed by adding approximately 0.5 gram of sodium oxalate. 

 After standing a short time the mixture was filtered through dry 

 filter paper and 10 c. c. of the clear solution used for the sugar deter- 

 mination. The method used for determining reducing sugars was a 

 combination of that of Bertrand (10), and that of Munson and 

 Walker (33, 56). In this method the cuprous oxid is determined by 

 titration, as in the Bertrand method, Fehling's solution and the' 

 time of heating are as specified by Munson and Walker. The Munson 

 and Walker tables were used for the sugar equivalents. 



Total sugars. — Fifty cubic centimeters of the solution used for 

 free reducing sugars were transferred to a 100 c. c. volumetric flask 

 and 5 c. c. of HC1 (sp. gr., 1.19) added. The mixture was set aside 

 over night and the flask made to volume at 20° C. the following morn- 



