The presence of even a very small portio of air materially retards the progress of th evaporation.
From the weight on the thirtieth day we fin 500 : 1000 : : 52.2 : x (= 104.4) sof contents, and 1000-104.4 = 895.6 water.
As a contrast to this evaporation in the remainder from 500 grs. was eva by water-bath, the temperature never above 180°F.
In 24 hours the residue weighed 48.4 48 46.9 72 46.1 96 46.0 By this time it had assumed a deep colour, and from being soft and sectile with the exception of a small portion i centre, become hard and brittle; by ex to the air it speedily deliquesced ; 30.6g the dry mass dissolved in water was with 16.7 grs. of yeast, which from th pomtion of another portion was found t tain 3.5 grs. of solid matter. The in. was set aside for four days at a tempemt 70° to ferment; gas was slowly disen, when fresh bubbles ceased to form, the tion was evaporated to dryness, and arum to 25.8 grs.; deducting 3.5 solid matters the yeast, we have an unferrnentable mass 22.3 grs. out of 30.6, shewing the quantity of sugar to have amounted to only 8.3 grs., instead of about 24.5 grs. The foregoing experiment shews the impossiliility of obtaining an accurate result if the solution be evaporated in air even at temperatures considerably below 200°. Diabetic sugar, in fact, loses by this treatment 5 equiva lents of water and becomes converted into a spe cies of caramel, insusceptible of fermentation.
To proceed, however, with the analysis : The salts were found by incineration to amount to 3.09 per 1000 parts of urine.
To determine the quantity of sugar, 250 grs. of the secretion were mixed with yeast and placed in a tall graduated jar capable of con taining 25 cubic inches; filled with mercury, and inverted in a basin holding that metal, The barometer stood at 30.33 The thermometer [ 72° F.
' Air in the jar, which accidentally entered during the act of inversion 1.00 cub. in. Quantity of fluid 1.45 cub. in.
: • Exterior levet of the mercury 12.33 inches below the interior level.
In three days fermentation was complete.
The barometer then stood at.... 30.34 The thermometer 80° Exterior level of the mercury 1.14 below that of the interior.
The quantity of gas amounted to 19.3 cub.in. - adding the bulk of the fluid ... 1.45 We obtain total gas 20.75 Correcting for pressure we obtain 30 : 30.34 - 1.14 : : 20.75 : x (= 20.1828) Correcting this again for the temperature, 528 : 508 : : 20.1828 : x (= 19.41) Subjecting 'the air which was in the jar at he commencement of the experiment4he ame corrections, in order to deduct, in For the temperature 520 : 508 : : 1 : x (= 0.9769) For the pressure 30 : 30.33-12.33 : : 0.9769 : x (= 0.586) 19.41-0.58 = 18.83 corrected volume of carbonic acid.
Now 100 : 18.83 : : 106.6 : x (= 20.072) total number of grs. of sugar in, 250 grs. of urine, and 250 : 1000 : : 20.072 : x (= 80.29) sugar. The urea was found by a separate analysis; 00 grs. were evaporated in vacuo, the residue ated with hot absolute alcohol (f.3f1). It s allowed to cool in order to deposit part of e sugar, then decanted ; this was repeated ve or four times. The alcoholic solutions • ere evaporated to dryness, re-dissolved in ater, and treated with oxalic acid and sub quently with chalk, observing the precautions ready enumerated : 1.06 grs. of prismatic i Jedles of nearly pure urea were obtained.
. 500 : 1000 : : 1.06 : x (.= 2.12) urea.
As a comparative experiment 500 grs. were Aaporated by the water-bath and nitric acid bstituted for the oxalic; only traces of crystals nitrate of urea were thus obtained ; a con elusive proof of the superior delicacy of the first method.
The syrupy residue after exhaustion with ab solute alcohol was treated-with rectified spirit as long as any thing dissolved : 2.15 grs. of saline matters, uric acid, mucus and matters soluble in water only were left. 'Hydrochloric acid left only 0.04 of uric acid and mucus.
500 : 1000 : : 0.04 : x (= 0.08) uric acid, 4-c.
The, acid solution evaporated to dryness and incinerated, gave 0.69 grs.