328 Mr. Everitt on Garden Rhubarb as a Source of Malic Acid. 



devising of a process for obtaining the principal ingredients 

 pure, a difficult analytical problem. The details of the pre- 

 liminary experiments (which occupied some time) for finding 

 out what I had to deal with, would be both tedious and use- 

 less ; I proceed, therefore, to give a summary of the method 

 I adopted for the analysis of this substance, and of the best 

 means of proceeding, if the extraction of malic acid be the 

 only object. The stalks should have the cuticle taken off, as 

 it would introduce a great deal of colouring matter if put into 

 the press ; the peeled stalks are cut into small pieces about an 

 inch long, put into a strong canvas bag, and then subjected 

 to a great pressure ; by this means 20,000 grains of peeled 

 stalks yielded 12,500 grains of juice, and left 3850 grains of 

 damp fibre, which well washed and dried at 212°, weighed 

 800 grains, and is equal to 4 per cent, ligneous fibre. The 

 liquid had a light green colour, was very acid, its density varied 

 with the size of the stalks and the time elapsed since they were 

 cut, it also varied in the same specimen at different periods of 

 the pressing ; that which flows first I have had as low as 

 1-015, rising to that last yielded 1-022. 



I tried how much pure carbonate of soda and carbonate of 

 potassa were required to saturate a definite quantity ; but as 

 it afterwards was found to contain two or three acids, and 

 some salts of soda and potassa also present, these results are 

 of no use for determining the quantity of free acid. Some 

 pure crystals of carbonate of lime were made into a neutral 

 nitrate ; chloride of calcium being avoided as in a subsequent 

 stage chloride of lead, and hydrochloric acid would be formed, 

 to get rid of which would have complicated the process. 



To several pints of the juice bicarbonate of potassa was 

 added, this salt being used because it is much purer than the 

 carbonate, until all acidity was neutralized : a small quantity 

 of greenish pulpy matter made its appeai-ance, which was 

 separated by a cloth filter, and the liquid became much less 

 coloured: 4000 grains measure, specific gravity 1-01 2, required 

 65 grains of crystallized bicarbonate potassa for neutralization: 

 4000 at 1-023 required 93 of the same for neutralization: 

 nitrate of lime was now added and the solution boiled : this 

 is necessary, because oxalate of Jime, when precipitated cold 

 and thrown on a paper filter without boiling, passes through ; 

 moreovei*, malate of lime requires only 65 parts of boiling 

 water to hold it in solution. I found the separation of the 

 oxalic acid perfect by these means, while all the malates re- 

 mained in solution. The oxalate of lime collected on the 

 filter, amounted to 24*2 grains, dried at 212°, or the proto- 

 hydrate. It was tested in the usual way of boiling with ex- 



