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An Excerpt from Lavoisier's Laboratorv Journal J

RALPH E. OESPER University of Cincinnati, Cincinnati, Ohio


ONE of Lavoisier's studies has been more publiclzed . than his cyclic analysis and synthesis of air. This clever use of mercury and mercuric oxide has come to be known as "Lavoisier's Experiment fiar excellence." "This is the most complete proof that can be accomplished in chemistry," declared he, and the justness of this appraisal is manifested by the regularity with which this experiment is held up as a model. Even the beginners in chemistry are made familiar with this masterly cross-examination of Nature. Long after they have forgotten the details of the experiment or its objective, many chemists retain a mental picture of the apparatus: the furnace and the retort with its curved neck extending into a bell jar (Figure 1). The printed accounts of this study' are records of experiments for which the original notes are no longer preserved, or, more likely, these accounts are compiled from combinations of several trials, for Lavoisier admitted that "it is difficult in one experiment both to preserve the whole air upon which we operate and to collect the whole of the red particles, or calx of mercury, which is formed during the calcination." Neit6er the formation nor decomposition of mercury oxide. were original with Lavoisier; his merit consisted in combining them.

tory journals, preserved in Paris in the archives of the Academic des Sciences. Berthelot, in his abstract of these notebooks, states that this volume was less regularly kept than its forer~nners,~ and Lavoisier's own

From French. "The Dromo of Ckrmidry." Coarirrs of The Univcrrily Sociciy,Nclu Y o r k .



The entries in his laboratory journal referring to this experiment patently correspond to his fist attempt. The account is not complete, the work is exploratory, some of the measurements are on a loose sheet between the pages of the notebook,a half page was left blank for future entries that were never made. The experiment was carried out in April, 1776, and the memoranda are set down in Volume IV of his laboraMemoires de l'Acadmie des sciences, annCe 1777, 185 (1780), reproduced in "Oeuvres de Lavoisier," Vol. 2, 1862, p. 174; LAvorsrEn, "Trait6 &mentaire de chimie," 1789, p. 35, reproduced in "Oeuvres," Vol. 1, 1864, p. 36.

record states that he was obllged to interrupt this experiment because of a change of residence (to the Arsenal). Despite the fragmentary character of these notes, they have great sentimental, if not historic, interest because they are apparently the only remaining original record of the most famous of his experiments. This fact justifies the publication of notes that were never intended for the public eye. Furthermore, a glimpse behind the scenes is usually alluring, often enlightening, and sometimes disillusioning. A glance a t Lavoisier's sketches demonstrates why he did not make the plates for his Traitd, a task that was admirably accomplished by Madame Lavoisier. His handwriting is not easy to read, and considerable study BERTHELOT, "La revolution chimique," Paris, 1890, p. 289.


is required to decipher some of the words; a reading glass is a great aid. Though he used modem French


the record will be given here, with a hope that these samples may serve as a guide to those students who may wish to test their linguistic skill by reading the only known private account of Lavoisier's great experiment. On the pages between those reproduced here Lavoisier records that on the morning of the 10th. the absorption seemed to have ceased, 48 hours later more calx appeared, after 80-100 hours its quantity was rather considerable. At this point he stopped the heating because of the move into his new residence. He found the residual air extinguished a flame but gave with nitrous air (nitric oxide) a little red vapor, six volumes of the air and one volume of oxide shrank to 5'/*. The residual air mixed with dephlogisticated air (oxygen), which he knew to be not more than fifty per cent pure, was tested with a flame; 8:l extinguished, 5:l supported the flame about as well as ordinary air. Two volumes of this mixture with one volume of nitrous air shrank to 15/o; three volumes plus one volume gave 3'/4, but even this mixture contained an excess of nitrous air because the addition of a little common air produced red fumes. The air from the calcination gave no precipitate with lime water. These items show how uncertain he was a t the time of this first study in contrast to the assuredness he exhibited in his later reports. The story of the evolution of his antiphlogistic ideas has been told too often to need repefition here.


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