Application of the fluids.-20.0 c.c. of fresh filtered urine are put into a glass or china dish of four inches in diameter, and one inch in height. A triangle, made of a glass rod, is now put across the top of this dish, to support a smaller flat dish containing 100 c.c. of the standard sulphuric acid. This is now placed under a receiver on a ground-glass plate, closed hermetically by the aid of tallow. A dinner-plate and some mercury may also be used for the purpose. When the entire apparatus is thus completed, 100 c.c. of milk of lime are added to the urine in the lower dish, and the apparatus is quickly closed and put aside. After the lapse of fortyeight hours the whole of the ammonia formerly contained in the urine will be found to have been driven out, and to have been absorbed by the sulphuric acid in the upper dish. If the sulphuric acid is now neutralized by the standard solution of soda, so much less of this solution is required as is equivalent to the amount of ammonia contained in the acid. Thus, if the 10 c.c. of sulphuric acid (containing 0-505 grammes of SO, corresponding to 0:21 16 grammes of NH), after exposure to the vapour of ammonia evolved from the urine under the glass shade, require only 26 c.c. of the solution of soda instead of the 30 c.c. for which they are graduated, they have absorbed an amount of ammonia equivalent to 4 c.c. of the solution of soda, of which it has been seen that every cubic 0.2146

centimètre corresponded to

30

0.00715 grammes of

NH. The 20 c.c. of urine, therefore, evolved or contained 4 × 0·00715 = 0·0286 grammes of NH. 1000 grammes of urine would therefore contain 113 grammes of NH; and every other quantity in proportion.

Neubauer found that healthy fresh urine, free from mucus, does not undergo alkaline decomposition during the first forty-eight hours after being passed. But it is not so with the urine from patients, which very frequently begins to decompose a few hours after emission. Such urine, therefore, requires some precautions; and of these, the first to be noticed is the advice of Vogel, to empty the bladder by means of the catheter, and then to collect the freshly secreted urine through the catheter, which is left in the urinary passages. The urine is thus protected from the decomposing influences, both of the secretions of the bladder and of the higher temperature of the body. If this precaution be not feasible, the colouring and other easily decomposing matters may be removed by means of a mixture of equal volumes of solutions of basic and of neutral acetate of lead. Of this mixture 30 c.c.

are mixed with an equal volume of urine, and of the liquid filtered from the precipitate 40 c.c., corresponding to 20 c.c. of urine, are taken for the analysis of ammonia. If the operator will take a little more trouble, he may control the analysis performed with milk of lime, by putting urine into a second apparatus without it. If the latter evolve no ammonia, spontaneous decomposition of the urine has probably not taken place.

The method of finding the amount of ammonia in urine by means of chloride of platinum, given by Heintz, requires so much time for its execution that it becomes simply impracticable. In that respect it shares the fate of the analysis of urea by the same indefatigable observer; but there is that difference, that the analysis for urea gives an accurate result for the trouble, of which we are not sure regarding ammonia, for reasons already advanced. It is therefore not to be wondered at, that the amount of ammonia found by Heintz in the urine of twenty-four hours should be more than double the quantity of that found by the above analysis of Neubauer, a fact which adds to the probability that chloride of platinum produces ammonia in urine by decomposition of some of its constituents, not being simple salts of ammonia.

Quantity of Ammonia discharged in the Urine during twentyfour hours by healthy individuals.

Neubauer examined the urine of two male individuals of twenty and thirty-six years of age respectively. The average of twelve analyses of the urine of the man of twenty years gave 06137 grammes of ammonia for twenty-four hours. The average of the second subject, as found by the same number of analyses, was much higher than that of the first, namely, 0.8351 grammes of ammonia for twenty-four hours. The minimum was 0.3125; the maximum 1·2096 grammes of ammonia each day. Expressing these facts in round figures, we may say that the average amount of ammonia excreted by a healthy man is, minimum, 03; average, 07; maximum, 10 gramme.

Physiological origin of Ammonia.

The only reliable knowledge on this point consists in the following facts: The ammonia of the salts of ammonia, when the latter are taken into the stomach, passes unchanged through the system and is discharged in the urine. This has been proved beyond doubt by the analyses of Neubauer.1 The Journal für Practische Chemie,' Bd. 64, p. 281.

4

subject of his experiments was the young man of twenty years of age, whose average discharge of ammonia during one of twelve days had been ascertained to be 0-6137 grammes. He took now 2 grammes of hydrochlorate of ammonia in a glass of water for five successive nights; and, in the urine collected for five successive periods of twenty-four hours, analysis showed an excess of 9'957 grammes of hydrochlorate of ammonia over the amount of ammonia previously ascertained to be the normal average.

It remains to be seen whether caustic ammonia and carbonate of ammonia are eliminated in a similar manner. It remains, also, to be ascertained whether the organism produces any ammonia under ordinary circumstances, or whether the ammonia in the urine is simply introduced by our food and drink, or by the air which we breathe. Some articles of food are rich in ammonia, e. g., radishes. The smoke of tobacco contains a large share of ammonia; and any person remaining for any length of time in a room filled with this ambrosial offering to Apollo, must inhale such quantities of ammonia as must materially increase the ordinary amount in his urine. If ammonia be really essential to the blood, the anti-tobacco leaguers may yet hear the argument advanced, that tobacco smoking is really essential to keep our fibrine in solution, and that smoking has of late become so much more common, because the ordinary sources of this "food," the cesspools, dunghills, and other like accompaniments of human and animal habitations, have been done away with. A still greater amount of ammonia is of necessity inhaled where both the sources just mentioned flow without restraint.

Pathological indications.

If what some have ventured to bring forward as a defined feature of certain forms of disease of the kidney can really be maintained, namely, that the urea retained in the blood may there undergo decomposition into carbonate of ammonia, and give rise to the symptoms described as uremia, the pathological indications of ammonia in the urine would be all important in those diseases. And though quantities of ammonia might be excreted by the lungs, skin, and bowels, yet the urine would be that excretion in which the ammonia would be most accessible to our analysis. However probable such a process, under given circumstances may be, actual and direct proof would be required to make it a fact; and this we cannot say to have been afforded by the originators of the theory. We know,

on the contrary, that the test said to be diagnostic of the presence of ammonia in the breath, the formation of white vapours on contact of the breath with a glass rod dipped in hydrochloric acid, frequently fails in cases with the most marked symptoms of uræmia. We must, therefore, expect further proofs, analyses of the blood and the excretions, before we can give that extension to toxæmia as a cause of various severe affections, which by various authors has been attributed to it. It is the same with putrid or septic fevers, under those conditions in which the blood is said to be in a state of dissolution. For all we know, ammonia may be a product of these pathological processes; and then we might expect to find it, in part at least, in the urine.

If urine is ammoniacal, and we should wish to determine the amount of ammonia thus formed from urea, we may precipitate the ammonia by the addition to a measured quantity of a salt of magnesia. If the mixture is well stirred for a little while, the triple phosphate thus formed will subside, and by its weight, when in the form of pyrophosphate, the amount of free ammonia contained in the urine may be calculated. But this analysis should not be depended upon for any very accurate conclusions, as the sources of error surrounding it are numerous.

'Schmidt, Krystallonomische Untersuchungen,' p. 55.

THERE is a little carbonic acid in the urine, as in most animal fluids; and a method has been devised by Marchand1 for determining its quantity. From a measured quantity of urine the carbonic acid is evolved by warmth and diminished air pressure, and caught in baryta water. This is the principle of the analysis; the following are the particulars: 100 c.c. of urine are put into a balloon, closed by a cork, which is pierced by two glass tubes. One tube dips into the urine, and above the cork is drawn out into a long point, and closed by the blow-pipe. The second tube begins with the cork, has a double bend, and is connected with a second, but empty bottle, out of which a second doubly bent tube leads to a third balloon, half full of clear baryta water. Several bottles with baryta water may yet be attached. To the last one the air-pump is fixed. The whole apparatus being made airtight, the balloon containing the urine is placed in the waterbath, and its temperature raised to 112° or 140° F., after which the air is gently pumped out of the apparatus. The urine soon begins to boil, and distils partly into the empty bottle, and the solution of baryta in the several bottles becomes turbid from carbonate of baryta. After the lapse of about half an hour or more, the thin point of the first tube is broken off, and air is gently drawn through the apparatus. The carbonate of baryta is afterwards separated by filtration, washed, and dissolved in hydrochloric acid; the solution is precipitated by sulphuric acid; and from the weight of sulphate of baryta thus obtained the amount of carbonic acid is calculated.