1 '
II
Correspondence
ijl
i
PARACELSUS AND THE DISCOVERY OF HYDROGEN DEAREDITOR: In the paperby Mary Elvira Weeks on "The Discoveryof the Elements. IV. Three Important Gases," published in the February, 1932, number of THIS JOURNAL,^ the extremely questionable statement is revived in connection with the discovery of hydrogen, that Paracelsus "noticed the effervescence that occurs when iron is treated with dilute sulfuric acid, and mentioned in his 'Archidoxa' that 'Luft erhebt sich und bricht herfdir gleichwie ein Wind,' " reference being made to Ropp's "Geschichte der Chemie."2 Kopp in 1845 accepted the statement, without confirmation, on the authority of Hoefer, who gave it forth in his "Histoire de la Chimie,"3 quoting as reference Hnser's first edition (1589) of the Works of Parac e l ~ u s . ~Thirty years later, in dealing with the discovery of the composition of water, Kopp stateds that he could not then consult the edition of Paracelsus which Hoefer mentioned, but that in Huser's Strasburg edition of 1616 he was not able to find any confirmation of the statement, and he mentioned further that at the place in the "Archidoxa" from which the above quotation is derived, there is no mention of interaction of sulfuric acid with a metal, or of either of these substances themselves. This question is dealt with a t considerable length by Stillman6 who quotes the relative passage from Paracelsus and gives a translation of it, but this author, like Kopp, referred to the 1616 Huser edition and was therefore, presumably, unable to consult the 1589 edition. As it did not seem altogether satisfying to leave the matter without verification of the original reference, and with a view to putting Kopp's finding beyond all doubt, a photographic copy of the actual page referred to b y Hoefer, in the 1589 edition, was obtained from the Bodleian Library a t Oxford. Here is the passage concerned, copied letter for letter: J. CHEM.EDUC..9, 215 (1932). W O P P , "Geschichte der Chemie," 111, 1845, 260. WOEPER, "Histoire de la Chimie." 11, 1843, 16; 2nd edition, 11,1869, 12. "iicher uud Schriften des edlen, hochgelehrten, und bewehrten philasophi mcdici, Philippi Theophrasti Bombast von Hohenheim Paracelsi genannt; jetzt aufs neu aus den Originalien und Theophrasti eigener Handschrift, saviel dieselben zubekammen gewesen, aufs trefaichst und fleisigst an Tag gegeben, durch Joannem Huserum Brisgoium, Bae, 1589, Vol. 6. p. 12. KOPP, "Beitrige zur Geschichte der Chemie," Braunschweig, F. Vieweg und Sohn, 1875, 111, 241 (1875). STILLMAN, "The Story of Early Chemistry," D. Appleton & Co., New York City, 1924, pp. 357-60. 1122
'
VOL. 9, No. 6
CORRESPONDENCE
1123
S o merck das die Elementen i n der Scheidung gefunden werden gleich in der gestalt unnd form wie sie a n den wesentlichen Elementen seind. Dann der Lufft erzeiget sich gleich dem Lufft und ist nicht zu befassen als ettliche in ihren gemzittern vermeinen; A u s der ursachen das in dew Instrument der Scheydung der Lufft sich erhebt und herfzir bricht gleich wie ein W i n d unnd etwan mit Wasser aufffehret etwan Erdtrich etwan Fewer. Dann ein sondery wnderbarliche auffhebung ist im Lufft. Als wann auss dem wesentlichen Element Wasser sol1 der Lufft gescheiden werden als dann geschicht durch das sieden: Unnd sobald es seudt so scheidet sich der Lufft vom Wasser und nimpt mit sich die leichtist substantz vom Wasser: Unnd souil das Wasser gemindert wird also nach seiner Proportion und quantitet wird auch gemindert der Lufft. This passage is virtually, but not absolutely, identical with that quoted by Stillman. It may be translated as follows: Observe therefore that the elements are found in the separation the same in their shape and form as they are in the essential elements. For the air shows itself like air and is not to be grasped as some imagine in their minds. For the reason that in the instrument of separation the air arises and breaks forth like a wind and ascends perhaps with water, perhaps earth, perhaps fire. For there is a specially remarkable uprising in the air: as when, from the essential element water, air is t o be separated which takes place by boiling: And as soon as i t boils, the air separates from the water and takes with i t the lightest substance of the water: And as much as the water is diminished, the air, according to its proportion and quantity, is also diminished. With regard to the expression "Instrumentrder Scheydung" in the quotation, there is some doubt as to its significance. While it is rendered literally as "instrument of separation" in the above translation and is discussed by Stillman as possibly referring to "the operation of parting in assaying;" possibly meaning "only the separation of air from water by boiling," the opinion of Dr. 0. Schlapp, lately Professor of German in the University of Edinburgh, is that it really stands for "Moment der Scheydung" and, if so, the translation should read "at the moment of separation," which seems to fit in more appropriately with the context. Independent support for Professor Schlapp's opinion seems to be afforded by the fact that the word "Instanz" occurs, instead of "Instrument," in an earlier edition of Paracelsus, published at Strasburg in 1570.' The word which is printed "aufffehret" in the quotation, appears in Stillman's transcription as "aussfehret." In the 1589 original it has quite distinctly "ff followed by "f". The 1570 edition has "auffehrt." 'Archidom Philippi Theophrasti Paracelsi Bombast des hocherfahrnen unnd der Natur beriihmtesten Philosophi und bevder Arznei Doctoris von hevmligkevten . . . Zchm Ihwher Grtruckt ru S t r a s l u r x dwrh 'l'hcudosium Rihcl. \'orred. hliclmrl Toxites, fi1edicu.i Ar;rntorntrnris Gchen a u Stra4mrg den 2.1 J:tn : 1Xu Dns I 1 Buch. (This hook has no pagination: the passage concerned is on the eighth page.)
1124
JOURNAL OF CHEMICAL EDUCATION
JUNE,1932
In view of what is stated in the foregoing, it appears to be desirable that the assertion that Paracelsus observed the evolution of hydrogen during the interaction of sulfuric acid with iron or other metal should be permitted to disappear from current literature. LEONARD DOBBIN BLACKSHIELS, SCOTLAND
BALANCING CHEMICAL EQUATIONS DEAREDITOR: EDUCATION have The last few numbers of the JOURNAL OF CHEMICAL contained several letters concerning various methods of balancing oxidation-rkduction equations. Since the inquiry of A. W. S. Endslow U. CHEM.EDUC.,8, 2453 (Dec., 1931)l there have been nine letters on the snbject. Four of these make no attempt to give Mr. Endslow the information he asked for, namely, references to published work on the algebraic methods of balancing equations. Instead they give detailed methods of balancing equations which in most cases have long been known and used. All of the methods are based on the idea of arbitrarily assigning valences or oxidation numbers to individual atoms in the molecules which react and are produced. The equation is then balanced by considering the changes in valence which occur during the reaction. That such assignment is purely arbitrary from the point of view of balancing the equation may be shown by fixing the valence of, say, th$nitrogen and allowing that of the oxygen to change. The following equation results. 0
I
+l +5 -2
loses (2 X 3) +2
+6 -2
1
t i -5
+I -2
+ 8HNOs = 3Cu(NOa)n + ZNO + 4Hs0 I gains (3 X 2) 1
3Cu
One may assign any numbers whatever so long as the sum of all the valences equal zero for a compound or equal the charge if an ion is considered. The methods run into difficulties when such constituents as H,Oz, SCN-, NHpOH, etc., are present. Valences must be assigned to sulfur, carbon, nitrogen, etc., and this is often difficult, a t least for beginners. Jette and LaMer in their so-called "ion-electron" method [J. CHEM. E ~ u c .4, , 1021,11.58 (1927)l have avoided this difficulty by considering the loss or gain of electrons when an oxidation or reduction reaction takes place. Thus, for the above reaction,
+ ., + +
3Cu = 3Cu++ . 3(2e) 2NOa- f 8Hf = 2 N 0 4H20 - 2(3e) 3Cu ZNOs8Hf = 2 N 0 4H.O 3Cu++
+
+
+
oxidation reduction complete
