although it kept the blood fluid so long as the bottle in which it was contained was well corked, and possibly escaped when the bottle was uncorked, as the blood then coagulated. Moreover, the escape of water vapour from newly drawn blood is so copious, that the white fumes of chloride of ammonium, even if present, would be obscured by it. Some other more delicate tests were therefore required, and were instituted.

Formation of Ammonio-Chloride of Platinum. The first test used was the ordinary one for obtaining crystals of ammonio-chloride of platinum.

EXPERIMENT CCXCVI. Formation of Ammonio-Chloride of Platinum from Blood-Vapour. An apparatus was fitted up with a Wolf's bottle (A), as in the experiment

of transmitting blood-vapour through blood. free end of the long descending tube (D) the bellows (c) were attached. The free end of the short or exit tube

To the

(E) was connected with one of Liebig's potash-bulbs (F) charged with perfectly pure hydrochloric acid. The Wolf's bottle being two-thirds filled with freshly drawn blood, and quickly closed, the vapour arising from the blood was blown briskly through hydrochloric acid, until the blood was fully coagulated. The acid was poured into a clean evaporating dish, solution of perchloride of platinum was added to it, and the mixture was carefully evaporated in the water-bath. The result was a deposit of the crystalline salt of ammonio-chloride of platinum, which was afterwards well washed in a mixture of alcohol and ether.

EXPERIMENT CCXCVII. Formation of Ammonio- Chloride of Platinum from Blood-Vapour. On the day after making the above experiment, I repeated it. The blood was drawn from a bullock. The apparatus worked well, and a free amount of blood-vapour was driven through the acid. The result was more decisive than in the former experiment.

EXPERIMENT CCXCVIII. Formation of Ammonio-Chloride of Platinum from Blood-Vapour. This experiment was conducted in the same way as the preceding, the subject being a heifer. The result was well marked, in a copious formation of the yellow salt.

EXPERIMENT CCXCIX. Formation of Ammonio-Chloride of Platinum from Blood-Vapour. The blood of an ox was experimented on in the same manner, with a similar result: there was a copious deposit of the salt.

In all these experiments, the same quantity of blood was used; viz., one imperial quart. The current of air was gently kept up for five minutes after the blood had coagulated. The air made for itself channels in the clotted blood, and thus passed freely through it. The

amount of precipitate obtained varied. The first experiment yielded a little more than 3 grains; the second, 2.14 grains; the fourth as much as 4.7 grains. But as the amount of gaseous exhalation is greatest when the blood is first drawn, and as the blood used was caught in an open vessel, and transferred to another vessel, it is obvious that much of the vapour was lost.

EXPERIMENT CCC. Formation of Ammonio-Chloride of Platinum from Blood - Vapour. The experiment was repeated with the blood of a sheep; but, owing to the rapidity with which coagulation took place, not above half a pint could be introduced into the bottle. The current of air was at once set up, and continued for ten minutes. Notwithstanding the small quantity of blood, the amount of ammonio-chloride of platinum obtained was little inferior to that in the first experiment.

EXPERIMENT CCCI. Formation of Ammonio-Chloride of Platinum from Blood-Vapour. The experiment was repeated on the blood of another sheep with a similar result.

Formation of Microscopic Crystals of Chloride of Ammonium. While the preceding experiments were in progress, another test suggested itself; namely, the production of microscopic crystals of chloride of ammonium from bloodvapour, by means of hydrochloric acid. If a little pure dilute hydrochloric acid be placed in a microscope glass and held over solution of ammonia for a moment, and the glass be then gently warmed, a field of the microscopic crystals will be formed. The crystals take various appearances; and in the opposite sketch, taken from a group examined by a quarter-inch lens, the artist, Mr. Aldous, has very skilfully depicted them in all their varieties, some (A) being larger, and others (B) more minute.

[In order to apply this process safely to the detection of ammonia in blood-vapour, certain conditions are required. 1. The acid used must be distilled over twice, or even oftener, to secure its perfect purity. 2. Before being used, a little of it is to be placed on the microscope glass, evaporated to dryness, and examined by the microscope, to see that it contains no crystallisable substance. 3. In evaporating, the process must

B

be done cautiously and slowly. 4. As the crystals rapidly absorb water, they should be examined directly after experiment. 5. To prevent fallacy, another microscope glass, moistened with the same acid, should be held at a short distance from the blood experimented

on, dried, and examined for comparison. With these prcautions, the microscope test is at once as delicate as it is easy and satisfactory. I have tried various tests for ammonia since this first suggested itself; but return to it as comprising the advantages of every qualitative test with least trouble and disadvantage.]

EXPERIMENT CCCII. Formation of Chloride of Ammonium from Blood-Vapour. The vapour from the blood of a heifer was driven over from the Wolf's bottle, as in the preceding experiments; but the exit tube, instead of being connected with the potash-bulb, was terminated in another tube with a finely tapering point. The vapour

being driven briskly over from some freshly drawn blood, was directed by the fine end of the tube upon a thin layer of hydrochloric acid, placed in the cell of a