“se Ss 
— S 
OrR er 0 PRe 
of a newly-discovered vegetable Acid. 17 
a substance is produced, which shows no traces of nitric acid, 
yet unites and forms a soluble salt with lime, ‘it therefore is 
not the oxalic acid.” By some other experiments he found that 
an acid is produced “ which does not differ in the least from 
the properties of the apple acid, and is accordingly the same.” 
This acid he detected in a great variety of vegetable juices. 
Since that period, Vauquelin has extended the catalogue ; but 
of all other plants, it is most abundantly contained in the Sem- 
pervivum Tectorum. 
Scheele’s process for obtaining malic acid is as follows. 
“ Saturate the juice of apples, whether ripe or unripe, with car- 
bonate of potash ; add solution of acetate of lead until it cease 
to produce a precipitation. To the edulcorated precipitate, add 
as much dilute vitriolic acid, as is necessary to give the mixture 
a perfectly acid taste, without any sweetness*.” , 
There are several objections to this process, all of which seem 
to have considerable weight. In the preceding pages I have 
shown, that the juice of apples, whether ripe or unripe, always 
contains two acids of very different properties. By the above 
process these acids are not separated; they are in fact found in 
what is supposed to be the resulting pure malic acid, and it is 
impossible, without the most complicated processes, to obtain 
this substance in the insulated form. P 
The precipitation of the lead by means of sulphuric acid ap- 
pears to be objectionable. I have often attempted to adjust 
the proportion of the latter substance, so as to throw down all 
the lead, without leaving any free sulphuric acid but I uniformly 
failed: and it is evident that, if not impossible, it is exceedingly 
dificult and troublesome. 
Scheele also attempted to obtain malic acid from malate of 
lime, by means of sulphuric acid, but found ‘ the mode rather 
dificult, as the acid would not let the calx fall completely.” 
Vauquelin observed the same thing. 
The last process proposed by Scheele, is to distil equal parts 
of weak nitric acid and sugar, until the mixture become brown, 
which is a sign that all the nitrous acid has been abstracted: the 
oxalic acid formed, is to be separated by lime-water, and the 
remaining acid to be saturated with carbonate of lime. The so- 
lution is to be filtered, the filtered liquor to be mixed with alco- 
hol, and the coagulum thus obtained, is to be edulcorated with 
new portions of alcohol.~ The coagulum is then to be dissolved 
in water, and mixed with a solution of acetate of lead: a pre- 
cipitate falls, which is to be treated with sulphuric acid, in the 
manner already directed. 
No one who has not gone through this process, can fully con- 
* Crell’s Chemische Annal, 1785, vol. ii. 295, ; 
Vol. 47. No. 213, Jan. 1816. B ceive 
