Pettenkofer's sub

stance is a mixture of

with a little

kreatine.

reaction. By this means the zinc and hydrochloric acid are separated in an insoluble form, while the substance, formerly combined with them, remains in solution. This is now acted on with blood-charcoal, which removes a yellow colouring matter and a trace of oxide of lead, and the filtered liquid is evaporated to dryness.

By the process of Pettenkofer, as well as by that just described, there was obtained a white crystalline kreatinine substance, having, in each case, the same characters. But a closer investigation immediately showed that this substance was a mixture of two compounds of different properties, which may easily be separated by means of alcohol, one of them being easily soluble, the other very sparingly soluble, in hot alcohol. When a portion of the mixed substance is boiled with 8 or 10 times its weight of alcohol, either a part remains undissolved, or the solution is complete, but deposits crystals on cooling. These crystals are found to be identical with the undissolved residue. When they are separated from the mother liquor, and the latter evaporated, a new crystallisation, of different form and properties, is obtained. The body which crystallises first, or remains in the undissolved residue, contains water of crystallisation and has no action on vegetable colours; the more soluble has in its aqueous solution a strong alkaline reaction, its crystals do not effloresce when heated, and the analysis of these two compounds showed, as the external form and chemical characters indicated,

the com

from urine.

that the one which first crystallised was kreatine, the Analysis of other kreatinine. The kreatine thus prepared from pounds urine yielded, when burned with oxide of copper, a gaseous mixture containing, for 3 vols. of nitrogen, 8 vols. of carbonic acid.*

0.6085 gm. lost at 212°, 0-0775 gm. of water, = 12.77 per cent.

0.3686 gm. yielded 0-500 gm. of carbonic acid and 0.2348 gm. of water.

That ingredient of Pettenkofer's substance which was most soluble in alcohol (kreatinine) gave, when burned, a gaseous mixture in which nitrogen and carbonic acid were in the proportion of 280 N to 740 CO2, or of 3 vols. nitrogen to 8 vols. carbonic acid. Further, 0.3767 gm. of the same body yielded 0.589 gm. carbonic acid and 0-2112 gm.

Composition of the

The composition of these two substances in 100

substances parts is therefore,

from urine.

They are identical

with krea

tine and

If we compare these numbers with those obtained by the analysis of kreatine from flesh, and the kreatinine. analysis of the kreatinine prepared from it, it is obvious that they are respectively identical, and indeed no difference can be detected in the physical and chemical characters of the two substances from urine and those from flesh.

In the putrefaction of urine, the kreatine alone disappears.

It has been stated, that the two substances, which served for the preceding analysis, were obtained from fresh urine; but it seemed to me to be interesting, to ascertain the influence which the putrefaction of the urine has on these substances.

When putrid urine, in which, of course, all the urea has been converted into carbonate of ammonia, is boiled with milk of lime till ammonia is no longer disengaged, then filtered, evaporated to a thin syrup, and in this state mixed with chloride of zinc, there separates in the course of a few days a considerable quantity of a yellow granular compound, which contains chlorine and zinc, and under the microscope cannot be distinguished from the compound formed by chloride of zinc in fresh urine. When dissolved

FORMATION OF PETTENKOFER'S COMPOUND.

65

in boiling water, and deprived of chloride of zinc and colouring matter by means of hydrated oxide of lead and blood-charcoal, the organic substance contained in it was found to be kreatinine, without a trace of kreatine.

During the putrefaction of urine, therefore, the kreatine is destroyed, while the kreatinine suffers no change.

I consider kreatine to be an accidental and variable ingredient of Pettenkofer's zinc compound; for a warm (not boiling) solution of kreatine is not precipitated by chloride of zinc, and the crystals which are deposited contain neither zinc nor chlorine, but possess all the characters of pure kreatine.

of Petten

It is clear that if the fresh urine contain kreati- Formation nine in combination with an acid, and free kreatine, kofer's the kreatinine, when it is neutralised by an alkali, compound. will be set free, and when the liquid is concentrated to th of its original volume, the addition of chloride of zinc will precipitate the compound of chloride of zinc with kreatine; but the crystals of this substance will be mixed with those of kreatine, whenever the quantity of kreatine present is more than the liquid can retain in solution when cold.

I

economical source of kreatine

Although the amount of kreatine and kreatinine, Urine is an to be obtained from urine, is not considerable, yet consider the preparation of these substances from and kreatiurine to be more convenient, and especially more

F

nine.

Hydrochlorate of

economical, than their extraction from flesh; and by either of the processes just described, they may be obtained in any required quantity by operating on a sufficiently large scale.

Hydrochlorate of Kreatinine.-This salt, the prekreatinine. paration of which has been already described, dissolves readily in boiling alcohol, and crystallises from it in short, transparent, colourless prisms, very soluble in water; it is obtained by evaporating its aqueous solution in broad transparent scales of an acid reaction. A saturated solution of this salt in boiling alcohol, to which ammonia is added till the acid reaction is destroyed, deposits on cooling small transparent granular crystals of kreatinine.

0.4764 gm. of hydrochlorate of kreatinine yielded 0.5677 gm. carbonic acid and 0.227 water.

Further, 0-542 gm. yielded 0·513 gm. chloride of silver. This gives in 100 parts,

Double

salt with bichloride

of platinum.

Chloride of Platinum with hydrochlorate of kreati

nine. A solution of hydrochlorate of kreatinine gives, on the addition of bichloride of platinum, and

gentle evaporation, aurora-red prisms of the double