436 On the Nature arid Combinations 



the property of crystallizing, like that prepared from apple 

 juice. I accordingly poured on it different portions of boiling 

 water, which were received in different vessels: the washings 

 were all of a brownish-yellow colour, from a small quantity of 

 nialate of lead held dissolved. At the end of 4S hours this salt 

 was all deposited in the state of a brown subtile powder, but 

 there was no formation whatever of crystals. On the surface of 

 each washing was an iridescent pellicle of some lustre, which I 

 found to be characteristic of the malic acid. This experiment, 

 as Scheele directs, was made with weak nitric acid ; I repeated 

 it with an acid of considerable strength, but after sixty hours 

 there was not one crystal. 



It deserves attention, that the matter which remained on the 

 filter in these two experiments, after washing with boiling water, 

 were as soft and jiasty as when first collected ; whereas the salt 

 of lead obtained from the berries of the Sorbus had grown dense, 

 hard, and was much diminished. 



The saturnine compound that had been formerly obtained 

 from the berries, when partially decomposed by sulphuric acid, 

 afforded crvstals on cooling. In order to ascertain if the malate 

 of lead obtained from sugar would do the same, I repeated the 

 jirocess on it, but obtained no crystals, — These experiments were 

 made under almost every possible circumstance with the same 

 results. 



I next precipitated all the lead from the remaining malate : 

 the malic acid tluis obtained was again mixed with acetate of 

 lead, and tlie precipitate treated with boiling water as before : 

 but the residts were the same. From this malate of lead the 

 acid was again separated, and the same process as before was 

 four times repeated : but notwithstanding nearly all the foreign 

 matter was thus separated, no crystals formed. 



Scheele found tliat the gooseberry contains nearly equal parts 

 of citiic and malic acids. I thought it necessary to examine if 

 this fruit would afford crystals. Scheele's process for separating 

 the acids is as follows : The juice is to be evaporated to the 

 consistence of honey, the pure acid to be separated by alcohol, 

 and the alcohol to be finally evaporated. The residuum is to be 

 dissolved in water, satuVated with carbonate of hme; the solu- 

 tion is to be filtered, and boiled so as to separate the citrate of 

 lime. The remaining brown solution is malate of lime : the salt 

 is to be precipitated by alcohol, redissolved after edulcoration, 

 and the solution is to be precipitated with acetate of lead*. All 

 this 1 followed : :3ut after treating the malate of lead with boiling 

 water, I obtained no crystals. 



* Crell'g Chemixhe Annul. 1785, vol. ii. 21?2. 



The 



