NOTES ON LEMON-JUICE AND ITS DECOMPOSITION. 
205 
Then, after passing through the intermediate stage of aldehyde, 
4(C 2 H 6 0) -f 80= 4(C 2 H 4 0 2 ) + 4H.0 
Alcohol. Acetic Acid. 
This result you have before you on the table. 
On examining a vessel containing a large quantity of lemon-juice, the 
peculiar earthy smell of carbonic acid is distinctly perceptible. For a clearer 
proof, a quantity of juice was put into a bottle which was connected by a 
glass tube with lime water, beneath which the glass tube dipped ; all was 
hermetically sealed and laid aside, when the deposition of carbonate of cal¬ 
cium became sufficiently evident. 
The decomposition would be explained thus :— 
3(C 6 H 8 0 7 ) + 30 = C 12 H 24 0 12 + 6 C0 2 
Citric Acid. Glucose. Carbonic Acid. 
This change is of course one example among many of the chemical trans¬ 
formations which take place in the maturation of fruits, and a striking one 
it is. 
Freshly expressed lemon-juice is a thin, milky, slightly yellowish liquid, 
having a sp. g. from T040 to 1*045, and containing from 39 to 46 grains oi 
citric acid per ounce. Should either of these be less, the lemons must have 
been kept too long or gathered too late in the season. 
Liquor potassse turns the juice a peculiar dark colour, well known to those 
accustomed to diabetic examinations. 
When freshly pressed the smell is aromatic, but when kept for a few days 
acquires the mouldy flavour which the commercial juice usually possesses. 
Trommer’s and Fehling’s tests give a decided indication of glucose. 
With polarized light the ray is turned to the right. Acetate of lead gives 
a muddy white precipitate (gummate of lead). 
Chloride of barium, nitrate or acetate of potassium, or chloride of calcium 
should give no precipitate, indicating the absence of sulphuric, tartaric, or 
oxalic acids. The aroma of the pure juice is very peculiar, and differs as 
much from any artificial compound as rose-water distilled from the petals 
does from that made with otto. 
The juice from limes is not so acid as that from lemons. 
Through the kindness of a friend I obtained a dozen limes from Glasgow, 
from these I obtained 5| ounces of juice. This was very much more aro¬ 
matic and more delicate in its flavour than lemon-juice. Its sp. g. was 1*037, 
and contained 32*22 grains per ounce. It was, therefore, not so strong as 
lemon-juice. 
Messrs. Southall, of Birmingham, furnished a sample as coming from the 
Olveston plantation in Montserrat, which had a deep yellowish-brown colour; 
this, I presume, was given artificially, as that pressed by myself from the 
fruit was nearly colourless. 
This coloration has since, however, been shown to have been accidental 
from the containing vessel. 
A singular fact was communicated to me by D. Davis, Esq., Medical In¬ 
spector for Bristol, which was (at any rate, to me) quite new. Of course, all 
chemists are aware that when citric acid is fused with potassa it is decom¬ 
posed into oxalic and acetic acids, thus:— 
C 6 H s 0 7 + H 2 0 = C 2 H 2 0 4 + C 2 H 4 0 2 . 
Citric Acid. Oxalic Acid. Acetic Acid. 
But when liquor potassse is mixed with common lemon-juice in the cold, 
oxalic acid may be detected in a few days. 
