CHANGES DURING THE SPOILAGE OF TOMATOES. 15 



gram of oxalic acid). Heated 15 minutes on a steam bath, added 1 

 gram of oxalic acid, and made strongly acid with sulphuric acid. To 

 titrate back required 4 cc of the potassium permanganate. Found 

 0.1003 gram instead of 0.100 gram. 



(b) Used 0.293 gram of tartaric acid in 100 cc of water, 3 grams of 

 sodium hydroxid, and enough potassium permanganate to produce a 

 blue-black color (about 1.8 gram). Heated 30 minutes on the steam 

 bath, added hydrogen peroxid to destroy excess of potassium per- 

 manganate, boiled to remove excess of hydrogen peroxid, filtered, 

 made the filtrate acid, and determined oxalic acid by titration with 

 potassium permanganate. Found 0.485 gram of oxalic acid instead 

 of the calculated amount, 0.492 gram; 98.5 per cent yield. 



(c) Used 10 cc of 1 per cent tartaric acid and 10 cc of concentrated 

 sulphuric acid. Potassium permanganate solution (8.4 cc = 0.5 gram 

 of oxalic acid) was run into the hot solution to a permanent pink color. 

 Required 5.3 cc; calculated for complete oxidation, 6.3 cc. 



o 



