Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 281

Another process for the quant.i.tative determination of sugar in urine, called by its author, Dr Roberts, "the differential density method," is based upon the loss of density, experienced by diabetic urine, after all the sugar has been removed by fermentation. Dr Roberts says repeated examples derived from diabetic urine so treated, together with corresponding experiments made with solutions of sugar of known strength in normal urine, and in pure water, as well as theoretical calculation have warranted the conclusion, _that the number of degrees of density so lost indicates as many grains of sugar per fluid ounce_.

The method, which is extremely simple, is thus performed:--Into a 12-ounce bottle measure 4 fluid ounces of the diabetic urine, and drop into it a piece of fresh German yeast, about as large as a cobnut or walnut; insert a cork in the bottle, and let the cork have a nick cut in the side, to allow of the escape of the carbonic acid. Then fill an ordinary 4-ounce bottle with the same sample of urine, omitting to add any yeast, and cork it in the ordinary manner. Place both bottles in a warm situation, where the temperature is about 80 or 90 Fahr., for twenty or twenty-four hours; at the end of which time, the fermentation being over, the sc.u.m will either have cleared off or subsided. The fermented urine is then poured into a proper urine-gla.s.s, and its specific gravity ascertained.

The specific gravity of the unfermented companion portion is also taken, and by comparing the two results the loss of density is thus arrived at.

Before the respective densities are taken it is best to remove the two samples to a cool place, where they should remain for two or three hours, in order that they may acquire the temperature of the surrounding air.

The two following examples may serve as ill.u.s.trations of the method.

I. II.

Density before fermentation 1053 1038 Density after fermentation 1004 1013 Degrees of density lost 49 25 ---- ---- Grains of sugar per fluid ounce 49 25

If it be desired to bring out the result as so much per cent., this is accomplished by multiplying the number indicating the "density lost" by the coefficient 023. Thus, in the first of the above examples, 49 023 = 1127; and in the second 25 023 = 569, which are amounts of sugar respectively per 100 parts.[250]

[Footnote 250: Roberts.]

In taking the densities Dr Roberts advises the operator to employ a urinometer having a long scale, since the degrees are much further apart than in the scales of the short-stemmed instruments, and are therefore more distinct and can be more easily read off.

The following are examples of diabetic urine:

No. 1 (Simon).

Specific gravity 1018 Water 95700 Solid const.i.tuents 4300 Urea Traces.

Uric acid Traces.

Sugar 3980 Extractive matter and } soluble salts } 210 Earthy phosphates 052 Alb.u.men Traces.

No. 2 (Dr Percy).

Specific gravity 1042 Water 89450 Solid const.i.tuents 10550 Urea 1216 Uric acid 016 Sugar 4012 Extractive matter, and} soluble salts } 5306

No. 3 (Bouchardat).

Water 83758 Solid const.i.tuents 16242 Urea 827 Uric acid Not isolated.

Sugar 13432 Extractive matters, and } soluble salts } 2034 Earthy phosphates 038

"Diabetic urine usually possesses a peculiar smell, which has been compared with that of violets, apples, new hay, whey, horses' urine, musk, and sour milk. Such comparisons serve only to show how difficult it is to give by description a correct idea of a particular odour. The colour of diabetic urine is generally pale. Sometimes, but not usually until after two or three days, the surface becomes coloured with a whitish film, owing to the development of the _sugar fungus_, and the _penicillium glauc.u.m_, and gradually the urine becomes opalescent in consequence of these fungi multiplying in great numbers in every part of the fluid. See URINARY DEPOSITS (FUNGI).

"Diabetic urine has a sweet taste, and often numbers of flies are attracted to it, which fact sometimes leads the patient to suspect that the urine is not healthy."[251]

[Footnote 251: 'Kidney Diseases, Urinary Deposits,' &c., Dr Lionel Beale.]

White merino, that has been wet with a solution of b.i.+.c.hloride of tin, is also said to form a ready test for sugar in urine.

Alb.u.men in urine may be detected by the nitric acid, or by the heat test.

The nitric acid test is performed as follows.--Fill a test tube to about an inch with the urine, then incline the tube and pour in strong nitric acid down the side of the tube, so that the acid sinks to the bottom and displaces the urine, which by reason of its smaller specific gravity rests above it. Let the acid be added till it forms a stratum about a quarter of an inch thick at the bottom.

If the urine contain alb.u.men three layers will be perceptible--one, perfectly colourless, of nitric acid at the bottom; immediately above this an opalescent zone of the coagulated alb.u.men; and, on the top, the unaltered urine.

In his work, 'Kidney Diseases and Urinary Deposits,' Dr Lionel Beale directs attention to the very important fact that "two or three drops of nitric acid to about a drachm of alb.u.minous urine in a test tube will produce a precipitate of alb.u.men which will be _dissolved on agitation_, while, on the other hand, about half as much strong nitric acid as there is of urine will redissolve the precipitate of alb.u.men, unless the quant.i.ty present be excessive. Alb.u.men precipitated by nitric acid is _soluble in weak nitric acid_, and in a considerable excess of urine, and it is also _soluble in strong nitric acid_. _It is therefore necessary in employing the nitric acid test to add from ten to fifteen drops of the strong acid to about a drachm of the urine suspected to contain alb.u.men._"

Dr Roberts gives the following directions for applying the heat test:--If the urine have its usual acid reaction it becomes turbid on boiling when it contains alb.u.men, and this turbidity persists after the addition of an acid. There are two points to be remembered on using heat alone as a test for alb.u.men. First, that alb.u.men is not coagulated by heat when the urine is alkaline; in such cases, therefore, it is necessary before boiling to restore the acidity by a few drops of acetic acid (carefully avoiding excess). Secondly, when the urine is neutral or very feebly acid, it may become turbid on heating, from precipitation of the earthy phosphates, but turbidity from this cause is easily distinguished from alb.u.men by a drop of nitric or acetic acid, which instantly causes the phosphates to disappear. It may sometimes happen that the patient whose urine is to be submitted to examination for alb.u.men may be taking large doses of nitric or hydrochloric acid. Under these circ.u.mstances Dr Bence Jones recommends the addition of ammonia to the urine, nearly to the point of neutralisation.

Mr Louis Siebold proposes a modification of Dr Roberts's method of applying the heat test in acid states of the urine, which is as follows:--Add solution of ammonia to the urine until just perceptibly alkaline, filter, and add diluted acetic acid very cautiously until the urine acquires a faint acid reaction, avoiding the use of a single drop more than is necessary. Now place equal quant.i.ties of this mixture into two test tubes of equal size, heat one of them to ebullition, and compare it with the cold sample contained in the other test tube. The least turbidity is thus distinctly observed, and gives absolute proof of the presence of alb.u.men, the error of confounding phosphates with alb.u.men being out of the question, as they are precipitated by the ammonia and removed by filtration.

M. Galipe[252] says the following is a delicate as well as trustworthy test for alb.u.minous urine. A few drops of the urine are carefully added to a solution of picric acid contained in a small conical test gla.s.s. If alb.u.men be present a well-marked turbidity will be produced at the point of contact between the two liquids. On applying heat the alb.u.men agglutinates, and rises to the surface. Phosphates and urates are said not to interfere with this test.

[Footnote 252: 'Pharm. Zeitung for Russland,' xiv, 48 ('Pharm. Journ.').]

In order to determine the quant.i.ty of alb.u.men in urine proceed as follows:--Add a little acetic acid to the urine, and then heat it in a water bath until it boils. Or the alb.u.minous urine may be dropped into boiling water acidulated with acetic acid. In either case collect the precipitate on a weighed filter, wash it well, dry it, and weigh it. The alb.u.men must afterwards be incinerated, and the resulting residue, which consists of earthy salts, must be deducted from the dried precipitate.

Stolnikow[253] adopts the following method for the quant.i.tative estimation of alb.u.men in urine:--The urine is diluted with water until a sample poured upon some nitric acid contained in a test tube produces still a faint white ring at the point of contact after the lapse of forty seconds.

The number of volumes of water added to the volume of urine (which may be taken as one) is divided by 250, and the quotient will be the percentage of alb.u.men in the urine. This relation has been established and confirmed by gravimetric determinations.

[Footnote 253: 'Chem. Central.' ('Pharm. Journ.').]

It is sometimes desirable to remove the alb.u.men from the urine before proceeding to search for other substances. There are several methods of accomplis.h.i.+ng this. If the urine be boiled the alb.u.men will become coagulated, but in many cases it may happen, owing to the urine being slightly alkaline or neutral, that a small quant.i.ty may remain in solution. Hence it will be advisable to add a little acetic acid to the urine before applying heat to it, to remove the precipitated matters by filtration, and to exactly neutralise the acid in the filtrate. If a few crystals of sulphate of soda be heated with alb.u.minous urine, the alb.u.men and allied matters may be entirely removed without injury to other organic matters dissolved, and without interfering with the employment of other reagents. When it is desirable to free the urine from alb.u.men previous to testing for sugar, this latter method will be found the best and most convenient.

The following a.n.a.lyses represent the amount of alb.u.men present in the urine of two patients suffering from Bright's disease:

No. 1 (Simon).

Specific gravity 1014 Water 96610 Solid const.i.tuents 3390 Urea 477 Uric acid 040 Fixed salts 804 Extractive matters 240 Alb.u.men 1800

No. 2 (Dr Percy).

Specific gravity 1020 Water 94682 Solid const.i.tuents 5318 Urea 768 Uric acid, and indeterminate } animal matter } 1752 Fixed soluble salts 520 Earthy phosphates 014 Alb.u.men 2264

Dr Parkes records the case of a patient suffering from alb.u.minuria, who excreted 545 grains of alb.u.men in twenty-four hours. See URATES.

Urine frequently contains an abnormally large quant.i.ty of urea. Such urine is of high specific gravity--1030 or more. When present in large excess the urea becomes deposited in 'sparkling crystalline lamellae' of the nitrate, if it be mixed with an equal quant.i.ty of strong nitric acid in the cold.

The crystals vary slightly in character, according to the amount of nitric acid employed and the degree of concentration of the urine. Urine which thus yields, without previous concentration, the nitrate, is said to contain an excess of urea. See page 1689.

The quant.i.ty of urea present in urine is best determined by a process invented by Liebig. When a solution of pernitrate of mercury is added to one of pure urea the urea and mercuric salt unite and form an insoluble compound, of undetermined const.i.tution. If, however, the chlorides of the alkalies and alkaline earths are present, this combination does not take place, owing to the decomposition of the mercuric nitrate, and the formation of b.i.+.c.hloride of mercury, and a nitrate of the alkali or alkaline earth, both of which are soluble. When, however, the decomposition of the chloride has been completed, the urea may be entirely precipitated, provided a sufficient quant.i.ty of mercuric nitrate be added to the solution. In estimating the amount of urea in urine, therefore, it is only necessary to add to the urine a solution of the mercuric salt of known strength, since from the quant.i.ty of this latter which has been employed in throwing down the urea, this can easily be calculated.

In performing this a.n.a.lysis, three special solutions are requisite:

1. A solution consisting of one part by measure of a cold saturated solution of barium nitrate with two parts (also by measure) of saturated baryta water. This serves for the removal of the phosphates and sulphates, the presence of which in the urine would interfere with the a.n.a.lysis.

2. The standard solution of mercuric nitrate, which is made as follows:--772 grains of red oxide of mercury placed in a beaker are dissolved in a sufficient quant.i.ty of nitric acid (sp. gr. 120) by a gentle heat, and evaporated over a water bath until all _excess of free acid_ is driven off. This may be known by the liquid becoming dense and syrupy in appearance. It is then poured into a properly graduated vessel and diluted to 10,000 grain-measures. Of this solution, 10 grain-measures = 01 grain of urea.

3. A solution of carbonate of soda in distilled water, 20 grains to the ounce. This solution is employed to indicate when the t.i.tration is complete, and to show the operator that all the urea has been precipitated by the mercuric salt.

The operation is thus performed:

(_a._) 400 grain-measures of the clear urine are mixed with 200 grain-measures of the baryta solution, No. 1. The mixture is poured into a filter, and of the clear filtrate which pa.s.ses through 150 grain-measures are carefully measured off, and poured into a small beaker. This quant.i.ty of course contains two thirds, or 100 grain-measures of wine.

(_b._) A graduated burette (each division of which equals a grain-measure of water) is next filled with the solution (No. 2) of mercuric nitrate, which is then dropped into the beaker containing the filtered urine, until the mixture becomes turbid. The quant.i.ty of solution that has been required to just reach the point of turbidity is then noted down; it shows that all the chloride of sodium has been decomposed, and that the urea is now beginning to precipitate.