ne 
1515.) : Royal Society. 63>, 
precipitate treated. with boiling water, as in the preceding case, 
yielded similar silky crystals; but the, substance remaining on the 
filter was a soft magma. Gooseberry juice treated in the same way 
yielded no crystals ; nor raspberry juice, nor the juice of elder ber- 
ries, nor of sedum tectorum, nor green apples. Thus it appears, 
that acetate of lead precipitates two different acids in the first two 
liquids. The first an acid not hitherto observed, which readily 
forms a supersalt with oxide of lead soluble in hot water; and this 
solution on cooling deposits the neutral salt in silky crystals: 
the second malic acid, which forms with oxide of lead a-salt not 
capable of crystallizing. ‘To obtain the new acid in astate of pu- 
rity, the colourless silky crystals are to be treated with a quantity 
of sulphuric acid capable of saturating the greater part, but not the 
' whole, of the oxide of Jead present. The liquid being filtered to 
separate the sulphate of lead, a current of sulphureted hydrogen is 
driven through it till the whole remaining oxide of lead is thrown 
down. The filtered liquid is now boiled for some time, and then 
exposed to the air for a few days to get rid of the sulphureted hy- 
drogen. 
On Thursday the Ist of June, Mr. Donovan’s paper was conti- 
nued. ‘To the acid thus obtained he gave the name of sorbic acid. 
It possesses the following properties. It is colourless. Its taste is 
intensely sour, and it reddens vegetable blues. It does not erystal- 
lize. 1t does not readily undergo spontaneous decomposition. Mr. 
Donovan kept a quantity of it in a phial for a year: no other 
change happened except the Ceposition of a very small quantity of 
mucilaginous matter. It combines with oxide of lead in three pro- 
portions, forming, 1. Subsorbate of lead, which is a hard white 
insoluble powder. 2. Sorbate, which may be obtained either in 
powder or in crystals, and which is likewise insoluble. 3. Super 
sorbate, which does not crystallize. The alkaline supersorbates may 
be all obtained in the state of crystals. It forms soluble salts with 
barytes, lime, and magnesia. Jt does not combine with alumina, 
These properties sufficiently distinguish this acid from the malic. 
Mr. Donovan likewise related his experiments on the preparation 
of malic acid. He found none of the methods recommended by 
Scheele capable of furnishing pure malic acid. - He considers Vau- 
quelin’s process for preparing malic acid from the juice of the se- 
dum tectorum as the only one that yields a tolerably pure acid. I 
may observe here, that about 10 years ago I made some experi- 
ments on the preparations of malic acid, and found that unless it 
be freed from mucilage before precipitation with lead, it cannot af- 
terwards be separated from a considerable quantity of gummy mat- 
ter which seems to fall down in combination with the lead. I as- 
cribe most of the difficulties which have occurred to chemists in 
preparing this acid, to not animadverting to this circumstance. 
Mr. Donovan conceives it likely that the bitter principle which 
exists at first in various fruits and disappears as they advance to ma- 
turity, may be the basis of some of the vegetable acids, 
E 2 
