Mr. Everitt on Garden Rhubarb as a Source of Malic Acid. 329 



cess of carbonate of soda or potassa, filtered, neutralized with 

 nitric acid, and precipitated by nitrate of silver ; the powder 

 dried and heated exploded feebly in the manner peculiar to 

 the oxalate of silver, leaving metallic silver. Nitrate of lead 

 was now added to the solution which had passed through the 

 filter from the oxalate of lime, and a copious bulky precipitate 

 was formed, which the next day, when it was cold, had formed 

 on its surface a few of the beautiful flat pearly crystals cha- 

 racteristic of malate of lead : it was brought to the boil, and 

 the malate of lead assumed a consistency like dough before 

 it goes into the oven ; and when that cooled it became as 

 brittle as resin. The liquid above the solid mass was decanted 

 and yielded good crystals on cooling. The whole malate of 

 lead was carefully washed and elutriated. About two-thirds 

 of it was acted on afterwards by sulphuric acid gently heated; 

 then separating the sulphate of lead by a filter, the remaining 

 third of malate lead was suspended in the liquid, and sulphu- 

 retted hydrogen passed through it till all the malic acid was 

 set free. This decomposition of some of it by sulphuretted 

 hydrogen, renders the solution sufficiently colourless, while 

 to do the whole in this way is very tedious. When operating 

 on several ounces, after filtration to collect the sulphuret of 

 lead, the free malic acid must be evaporated by a water or 

 steam bath to the thickness of syrup ; and it was only obtained 

 of the consistency of thick honey, by keeping it under the re- 

 ceiver of an air-pump, near the surface of oil of vitriol, for 

 nearly a week, occasionally taking out the capsule to warm it. 

 Some of the original juice, evaporated in the same way, yielded 

 beautiful crystals of binoxalate of potassa. 



After this the liquor still retained a small trace of citric 

 acid, which I obtained in a distinct form by taking advantage 

 of the difference of the solubility of malate and citrate of ba- 

 ryta. No tartaric could be detected. 



4000 grains of the original liquid evaporated and ignited 

 in platinum, yielded 29*2 grains of ashes, of which 

 28*4 grains were soluble in water, and 0*8 insoluble. 

 The solution of these 28*4 grains was alkaline, and required 

 12 real nitric, or 8*9 of sulphuric acid to neutralize it (these 

 two acids were used of an exact strength so as to contain 

 1 grain of real acid in 100 grains water measure). To the 

 neutral solution of the ashes in sulphuric acid nitrate of baryta 

 was added; a precipitate was formed, part of which was so- 

 luble on adding a little nitric acid, and turned out to be phos- 

 phate. The insoluble sulphate weighed 39*73 grains: no lime 

 salt was present. The nitric acid solution of the phosphate 

 evaporated to dryness left 4*4 grains j it was well tested and 



