The writer evidently wished to convey the impression—perhaps he himself believed—that these vials, which the professor had carefully prepared in his laboratory and showed to his friends after dinner, correctly exhibited the liquefaction in all its chief phases. If the liquid in the first vial had also several times changed its color; if it had filled the vial, not by adding bubbles to bubbles, but by an actual increase of the volume of the liquid within, independently of that frothing or bubbling; if it had then similarly decreased in bulk; if the liquid had solidified without any diminution of temperature, and become fluid again without increase of it, he would have presented a far stronger case than he has done.
But those points are absent. Perhaps the writer did not know that they were necessary. The letter itself is written in a jocular and mocking tone, and evidently in a spirit that relished sharp epigrammatic
points, calculated to excite a laugh, far more than the humdrum reality of sober truth.
We find another account of this same experiment in a French work before us: La Liquefaction du Sang de S. Janvier, by Postel. This account is more calm and sober in style, and is based upon the Bibliothèque Germanique, a work to which we have not access. It varies considerably from the sportive account given in the letter. According to Postel, the contents of the first vial liquefied entirely; the contents of the second vial liquefied only partially; in the third vial there was no change whatever. The statement is distinctly made that neither in the first vial nor in the second was there any sign of ebullition. The variation is important.
As between the two accounts, we could scarcely hesitate a moment which to hold most worthy of credit on any point on which they differed. In neither account do we find any indication of the nature of the chemical compounds which Dr. Neumann had prepared in his laboratory and placed in the vials. But as the experiment was made known and repeated, especially in France, we may take it for granted that the material used in those repetitions is the same that he devised.
This material is a mixture of suet, or other similar fatty matter, and ether, the compound being brought to any desired tint—in this case, a deep or dark red—by a further admixture of any suitable pigment. The mixture or compound so prepared is solid at ordinary temperatures; but at about 92° F. it will melt. If a quantity of such a mixture be inserted in a small glass vial, and the vial be clasped in the palm of one’s hand, it will soon receive from the hand sufficient heat to bring about a total
or a partial liquefaction, according to the greater or smaller proportion of the ether used in originally compounding it.
Neither would it be beyond the art of chemistry, in preparing this mixture, to introduce other ingredients, the particles of which would be brought into contact with each other when the liquefaction has been effected and the chemical combinations of which would then give rise to a greater or less amount of frothing or bubbles.
All this, however, is very far from being a reproduction of the liquefaction which is seen at Naples. The differences, or rather the failures to imitate and reproduce it, are essential and evident. We point out the chief ones:
I. This liquefaction of the laboratory always and entirely depends on the application of the proper degree of heat. So long as its temperature is below the melting point, the substance in the vial remains hard and unliquefied. When the temperature, from whatsoever cause, is raised above that degree, liquefaction ensues. If the temperature again sinks below it, the substance, if not meanwhile decomposed, returns to its previous solid condition. The operators themselves inform us frankly how the required degree of heat is usually communicated to it; by holding the vial, if small enough, in the palm of one hand, or tightly pressing it, if somewhat larger, between the palms of both hands. If the general heat of the room be raised high enough to reach the melting point of the substance in the vial, this circumstance alone would suffice to bring the compound to a fluid condition.