formed by the Action of the Nitric Acid. 1 9$ 



3. We may procure the mucous acid from the gum in 

 the same state of purity, by a very simple process, which 

 consists: 1st, in taking from it, by successive digestions in 

 very weak nitric acid, the whole of the oxalate of lime 

 which it contains: 2d, in boiling it in water, which dis- 

 solves it without dissolving the. flaky matter which the ni- 

 tric acid does not take up. 



4. When thus deprived of substances foreign to its na* 

 ture, the mucous acid of gum is entirely similar to that of 

 the sugar of milk, enjoys all the properties which charac- 

 terize this acid, and maybe employed with .the same advan- 

 tage in the most delicate experiments which require that 

 this acid should be of a perfect purity. 



I am convinced that there is a circumstance in which 

 the mucous acid obtained from gum is mixed with mucite 

 of lime, instead of the oxalate which I have mentioned. 

 This happens when we substitute in the preparation of the 

 mucous acid, the nitric acid diluted in water, instead of the 

 Concentrated nitric acid, and consequently when we con- 

 duct the operation slowly instead of hastily. It is easy to 

 ascertain the difference of the results which we obtain. 



If we employ the weak acid, the mucous acid is at first 

 produced alone, and it is precipitated, carrying with it the 

 lime, with which it forms a salt nearly insoluble, and we 

 may separate it from the mixture before the formation of 

 the oxalic acid, which requires the concentration of the 

 acid. If, on the contrary, we make use of concentrated 

 nitric acid, the formation of the two acids, although always 

 successive, is very thick ; and we may easily conceive that 

 in this case the oxalic acid, as soon as it is formed, seizes 

 the lime, in virtue of the more powerful affinity which it 

 exercises on this earth. 



I shall add another fact which led me to recognise a 

 singular property in mucous acid, which I intend to ex- 

 amine more in detail than I am able to do at present. 



When we gently evaporate to dryness the solution of 

 pure mucous acid made in boiling water, without separat- 

 ing the crystalline sediment which is formed during eva- 

 poration, we observe that the moment there is no more 

 liquid, the crystals become yellow, then brown, and are 

 converted into a viscous tenacious-like matter, which un- 

 dergoes a v kind of fusion, aud becomes very hard on cooling. 

 The mucous acid which has undergone this change, has a 

 much more acid taste than usual ; it. is infinitely more 

 soluble in water, — has become entirely soluble in alcohol, 

 and has therefore changed its properties in part. I thought 



N2 at 



