12 CHANGES DURING THE SPOILAGE OF TOMATOES. 



acid and 10 cc of 10 per cent oxalic acid added, and titrated with 

 the permanganate solution before described, 7.2 cc being required. 

 Found 0.2203 gram instead of the 0.221 gram added. 



(4) Ten cubic centimeters of lactic-acid solution containing 0.12 

 gram of lactic acid was made just alkaline to phenolphthalein and 

 heated on the steam bath for 10 minutes with 20 cc of potassium 

 permanganate solution (8.4 cc = 0.5 gram of oxalic acid). Five 

 grams of oxalic acid were added and titrafed with the permanganate 

 solution, 1.7 cc being required. Found 0.094 gram of lactic acid 

 instead of the 0.12 gram added. 



(5) To 0.12 gram of lactic acid in 10 cc of water were added 10 cc 

 of strong sulphuric acid, and the hot solution was titrated with potas- 

 sium permanganate until a pink color, persistent for 5 minutes, was 

 obtained. This required 5.8 cc of potassium permanganate solution 

 (8.4 cc = 0.5 gram oxalic acid). Calculated, 16.7 cc were required 

 for complete oxidation of the lactic acid. 



(6) Proceeded exactly as in experiment 5 except that the 0.12 gram 

 of lactic acid was dissolved in 100 cc of water. Required 4 cc of 

 potassium permanganate solution for titration. 



(7) A 10 cc lactic-acid solution containing 0.281 gram of lactic 

 acid was made strongly acid with concentrated sulphuric acid and 

 then titrated; 73 cc of potassium permanganate solution (69 cc = 0.5 

 gram of oxalic acid, H 2 C 3 O 4 + 2H 2 O) were required, and large amounts 

 of acetaldehyde were evolved during this titration. The amount of 

 permanganate required was 63 per cent of the theoretical necessary to 

 oxidize the lactic acid completely to carbon dioxid and water. Cal- 

 culation shows, however, that only one-fourth of this permanganate 

 would be necessary to oxidize the formic acid if the reaction is 



CH 3 CHOHCOOH->CH 3 CHO 4- HCOOH + O-+CH 3 CHO + CO 2 + H 2 O ; 



in fact much more permanganate was used than was necessary to 

 oxidize all the lactic acid to acetic acid and carbon dioxid, according 

 to the reaction 



CH 3 CHOHCOOH + O 2 -+CH 3 COOH + CO 2 . 



It is necessary to assume that under the conditions of this experi- 

 ment the lactic acid breaks down at once into small groups and not 

 alone into acetaldehyde and formic acid. 



(8) Twenty-five cubic centimeters of 1 per cent lactic acid and 25 

 cc of 5 per cent sulphuric acid were boiled and 20 cc distilled. No 

 acetaldehyde was found. To obtain the acetaldehyde it was neces- 

 sary to add manganese dioxid or some other similar oxidizing agent. 

 It is evident that the decomposition of lactic acid represented by the 

 equation 



CH 3 CHOHCOOH--CH 3 CHO + HCOOH 



does not take place as easily as is usually assumed. 



