380 Scientific Intelligence. 



In substituting the carbonate of soda for that of potash, taking the 

 crystallized salt in the same proportion as that above mentioned, a 

 very concentrated pectate may be obtained, which will furnish a very 

 white pectic acid, either by the addition of an acid or of some other 

 precipitating substance. To obtain the total quantity of the pectic 

 acid, new decoctions are to be made, with increased successive por- 

 tions of carbonate of soda. 



If to this gelatinous pectic acid, contained in a small platina cruci- 

 ble, there be added an excess of caustic potash, and the mass be 

 gently warmed and stirred, it soon becomes liquid and assumes a 

 brown color ; and if it be slowly evaporated, the saline matter which 

 remains in the crucible becomes, when the operation is well conduct- 

 ed and the heat carefully managed, speedily white. 



This white matter dissolves easily in water — the alkali is almost 

 entirely saturated, and if nitric acid be added to the solution until it 

 becomes slightly acid, we observe the disengagement of carbonic 

 acid, without any precipitation of the pectic. If nitrate of silver be 

 then added, an abundant precipitate of a granulated white powder 

 takes place, which exposed again to moisture and light becomes 

 slightly red. When this precipitate is treated with muriatic acid, it 

 produces chloride of silver, which, well washed, contains no vegeta- 

 ble matter. The washings, evaporated by a gentle heat, become 

 eventually of a light yellow, and some vapors of hydrochloric acid 

 are perceived. When the evaporation is completed, in a stove, per- 

 fectly white transparent crystals are formed without an atom of 

 mother water. They have the form of square columns, without 

 pyramids, some of them in groups. When dissolved, these crystals 

 precipitate lime water and all the soluble calcareous salts, properties 

 which clearly indicate oxalic acid. 



Of this remarkable transformation of pectic into oxalic acid, by 

 the influence of a weak alkaline action, two explanations may be ad- 

 mitted. 1. The action of an alkali may be assimilated to that of ni- 

 tric acid on the same body. It deranges its elements, and hence 

 arises a compound, which appears to be one of the last in the organic 

 scale — oxalic acid. 2. If we compare the chemical characters of 

 oxalic and pectic acids, we find often a near resemblance with res- 

 pect to the insolubility of their salts. We may admit that pectic acid 

 is a compound of oxalic acid and a gelatinous matter which is inti- 

 mately associated with it : the action of potash is hmited to the de- 

 struction of this gelatinous substance, and in combining with the ox- 



