£00 
its own bulk of carbonic acid at the observed 
temperature and pressure, we must in our cal- 
culations add the bulk of the liquid to that of 
the gas actually observed. Having reduced 
the bulk of gas to the standard ‘pressure of 30 
inches and the temperature of 60° F., accord- 
ing to the rules given in all works on physics, 
we deduce the quantity of sugar, since 100 
cubie inches of carbonic acid are furnished 
by the decomposition of 106°6 grs. of grape 
sugar. 
If mercury be not at hand, we may, by 
adapting a tube containing chloride of cal- 
cium, and a bulb apparatus charged with 
strong solution of potash,* the weight of which 
is accurately known, to a tubulated retort, ob- 
tain a result of considerable accuracy. Ina 
half-pint retort, so adjusted, 500 grs. of urine 
are placed, and 30 or 40 grs. of yeast added ; 
through the tubulure of the retort a straight 
tube passes, and dips below the surface of the 
fluid ; the upper extremity is closed by a cork, 
It is set aside to ferment at a temperature of 
70°; the chloride of calcium retains the mois- 
ture, and the potash ley absorbs the carbonic 
acid; by the increase of weight we know the 
quantity of carbonic acid formed. As at the 
close of the experiment the apparatus will be 
full of carbonic acid, it must be displaced by re- 
moving the cork from the straight tube passing 
through the tubulure of the retort, and then 
gently drawing air through the apparatus for 
some minutes by careful suction at the extre- 
mity of the potash apparatus, in the manner 
to be described presently when treating of the 
process of ultimate analysis. 100 grs. of car- 
bonic acid indicate 225 grs. of diabetic sugar. 
Another method of ascertaining the quantity 
of sugar consists in adding to a given quantity 
of the fluid a known weight of yeast—having 
by experiment determined the quantity of fixed 
matter contained both in the yeast and in the 
fluid operated on. After fermentation is com- 
plete the solution is evaporated to dryness, and 
the loss of solid matter sustained indicates the 
quantity of sugar which has passed off as alcohol 
and carbonic acid; the urea likewise is de- 
stroyed in the process, and its quantity must be 
deducted from the total loss. It is very desi- 
rable when sugar is present in considerable 
quantity that the evaporation to dryness should 
rformed in vacuo over sulphuric acid, as 
it is the only method that ensures our ob- 
taining the sugar always in the same state of 
hydration. This process, however, is tedious, 
always requiring many days for its completion : 
some comparative experiments, showing the 
een of this precaution, will be detailed here- 
r. 
Our methods of exactly determining the 
erie of sugar of milk are imperfect; I 
shall describe the plan which answers best 
when treating of the analysis of milk. 
Uric acid.—This is one of the most inte- 
resting and important animal products from the 
* These pieces of apparatus will be described in 
detail in the directions for the performance of ulti- 
mate analysis, 
ORGANIC ANALYSIS. 
part it frequently performs in some of the most 
serious and distressing diseases to which weare- 
hable. The method of detecting its presence 
by evaporation on glass with nitric acid has” 
already been described. When no albuminous 
principles are present, the solution is evapore 
to dryness and the residue treated with ; 
acidulated with hydrochloric acid; the inso- 
luble portion is dried and weighed, then 
burned ; the weight of the remaining ash 
(silica), if any, is deducted ; the loss indicates 
the quantity of uric acid. er 
robenzoic, or, as itis often called, hippur 
acid, has hitherto been found only in the urine, 
in which it generally exists in minute quantity 
according to Liebig. Its quantity may be a 
certained by adding hydrochloric oat to th 
liquid concentrated by evaporation. It is ey 
porated to dryness by a water heat, and th 
residue digested with pure anhydrous ether as 
long as any thing is dissolved. By spont: 
neous evaporation it is left behind nearly pun 
and may be weighed ; traces of urea c! ) 
with it, and a little of the odorous priney 
which obstinately adheres to it. If the eth 
have dissolved any fatty matter, the addition 
boiling water will dissolve the acid and lea 
the fats. Urobenzoic acid may be detected 
heating a crystal in a test tube; benzoic a 
and benzoate of ammonia, and a few red di 
of an oily matter, sublime, accompanied b 
smell of bitter almonds and of the Tonka 
Alcohol dissolves it freely, and the solutio 
evaporation leaves stellated groups of nee 
shaped crystals. With perchloride of — 
solutions of the urobenzoates furnish a ¢ 
mon brown precipitate. ‘ 
Lactic acid cannot be quantitatively ¢ 
mined without difficulty. The best me 
is as follows:—The solution if acid is” 
tralized with ammonia, evaporated to dry 
and the residue exhausted with alcohol 
the filtered liquid sulphuric acid is added | 
by drop as long as a precipitate ensues 
bases are thus removed as sulphates. The 
tion is filtered and the precipitate washed 
alcohol; the clear liquid is digested with 
Far agitation, at a moderate heat, for t 
our hours, with carbonate of lead: hydroe 
sulphuric, and phosphoric acids are thus 
rated as insoluble salts, while lactate of le 
solves. The solution is a second time fil 
sulphuretted hydrogen gas transmitted th 
the clear liquid, and the sulphuret of lead 
rated by another filtration; the filtered | 
evaporated to dryness to expel thealce 
cess of gas, the residue redissolved in 
digested with carbonate of zine ; by eva} 
of the filtered liquid crystals of lactate 
are obtained. If the solution is now 
with carbonate of potash in excess, eval 
to dryness, exhausted with boiling wal 
the residue dried and ignited, pure « 
zine is obtained: 100 grs. of this oxide 
202.5 grs. of lactic acid. , 
If oxalic acid be mies go" in any I 
must be super-saturated with lime wate 
treating the precipitate with acetie ac 
phosphates dissolve, and oxalate of Ii 
