Oxalic from other Organic Acids, 27 



could be thrown down by this means while the solution still 

 remained acid. 



1. If into solutions of acetic, tartaric, citric, carbazotic, 

 indigotic, benzoic, succinic, gallic, meconic, pyromeconic, 

 mucic, or camphoric acids, nitric acid be poured and after- 

 wards subacetate of lead, or if nitric acid be added largely 

 to solutions of acetate or nitrate of lead and solutions of these 

 acids be dropped in, the precipitate at first formed speedily 

 redissolves, and no further precipitate, crystalline or other- 

 wise, appears on standing for any length of time. I have not 

 tried any other organic acids, but the same is probably 

 true of many of them also. 



2. But if into a solution thus prepared, and containing al- 

 ready one or more of these acids, a few drops of a solution of 

 oxalic acid be introduced, crystals of the double salt begin to 

 appear. 



3. This is beautifully illustrated, and at the same time the 

 conversion of tartaric into oxalic acid, by dissolving the former 

 or the bitartrate of potash in dilute nitric acid; the solution 

 gives no precipitate with subacetate of lead, but boil it a little, 

 and a precipitate in shining crystals appears on adding the 

 salt of lead. This forms a very instructive class experiment. 

 Care must be taken to have the solution sufficiently acid, or 

 more or less of pure oxalate of lead will accompany the double 

 salt. 



4. 15*92 grs. of tartaric and 6*08 grs. of oxalic acid with 



one atom of water (C + H) were dissolved in a small quantity 



of water, and poured into an acid concentrated solution of 

 nitrate of lead in large excess. The double salt collected 

 and dried at 212° Fahr. weighed 45*03 grs., equivalent to 



6*14 grs. of (C+H). This indicates 0*06 of oxalic acid in 

 excess, an error which can hardly be avoided, from the im- 

 possibility of sufficiently washing the precipitate and filter 

 without risking decomposition. 



5. But the oxalic acid may also be separated from all these 

 other acids, and estimated with tolerable precision, without the 

 formation of the double salt. Thus 10 grs. of oxalic acid in 



crystals (C + 3 H), equivalent to 5*73 of anhydrous acid, were 

 mixed with 20 of tartaric acid, 10 of citric, 2 of benzoic, 4 of 

 succinic, and an unmeasured quantity of acetic acid dissolved 

 in two ounces of distilled water, and acid nitrate of lead added 

 to the solution. By this method of proceeding a sufficient 

 quantity of nitric acid was present to prevent the tartrate, 



