24 Bull. Hist. Chem. 12 (1992)
6 . . A. l, " r l t n d p v r r t t r v l tr t r l l r ", v nt f , 8 , 48, 60 6 . Ar t p nd r d d n p. 6 . h p p r, v r r l v nt f r nd r t nd n th d t n t n l nt t tr b t n h n th r nd th tr t r l th r f v n t ff, n v v d n f r th p t f l d nt n d n f tn t , t ll p r t n n 8 . 66. " n nt n r d l th r d rb n tr ", ll. S . Ch . ( r , 2 , , 4 6. 6 . Ib d., pp. 4. h r l v nt p rt f th r n l t xt r d : "... l d x rp rth .2 t .6 nt d nt t nd d pr v n t ff l rp .2 t l d bl l n ntr l rb n d t d ff r r d rp .6 ú l l l n pl ." (I v r r t f l t r f. . M h l M r d f r p nt n t th l l n n r n r n t n fr th pr nt: th l t .6 t r d .2 .
Dr. Leonello Paoloni is Professor of Chemistry in the Gruppo di Chimica Teorica, Dipartimento di Chimica-Fisica of the Universita Palermo, Via Archirafi 20,1-90123 Palermo, Italy. His main interest in the history of chemistry has been the approach to problems of molecular tr t r used by morpho- logical crystallography before the advent ofX-ray diffraction. More recently he has been studying the life and work of Stanislao Cannizzaro.
W ll d W ll t n ( 66 828 SOME EARLY CHEMICAL SLIDE RULES London that same year. A contemporary called it "an instru- ment which has contributed more to facilitate the general study William D. Williams, Harding University and practice of chemistry than any other invention of man" (3). It accelerated the acceptance of Dalton's atomic theory and An article by George Bodner in the Winter 1990 issue of the promoted chemistry as a mathematical science. Bulletin described a rare chemical slide rule designed by Lewis Only a few of these original slide rules are still in existence. C. Beck and Joseph Henry - their little-known "Improved Some are in European museums (4). Only two are known to Scale of Chemical Equivalents" (1). The reader is urged to have survived in the United States and both are located at review that description. The present paper attempts to place Harvard University. They are described as (5): this slide rule in context by describing its origins, as well as some of its predecessors and successors. n p p r l b l . f h 2 n. In r. n f : Ch l The concept of "A Synoptic Scale of Chemical Equiva- E v l nt l t f l nt nd p nd bl h d b W. lents" was first presented in 1814 by the English chemist, C r , 82 Str nd, n. , 8 4. On l d r: r d t d, n b r d William Hyde Wollaston (2). Chemical substances were l . On b : Sp l App nt nt [ r ] h n , arranged on a scale with distances proportional to the loga- ( p l f d n. AS O OMICA nd ph l ph l rithm of their equivalent or combining weights, much as the I S UME MAKE l hn h f value of pi was marked on the scales of the more conventional Cl r n 62 Ch r n Cr , O O . slide rules of recent memory. A logarithmic slider, numbered from 10 to 320, allowed quick calculation, via the method of Drawings and discussions of the Wollaston slide rule direct and inverse proportions, of the weights of substances appeared in several early American chemistry texts (6). reacting with one another, the quantity of products, or the Wollaston used oxygen = 10 as his equivalent (atomic) weight relative proportions of elements in a compound. Wollaston's standard, but his choice was not accepted by all of his contem- original design, measuring 12 by 2.5 inches, was marketed in poraries. Thomas Thomson observed that Dalton, Philips, Bull. Hist. Chem. 2 (1992) 25
Henry and Turner preferred hydrogen = 1 as their standard, while he, Wollaston, Berzelius and "the greater number, if not the whole, of chemists on the continent" used oxygen = 1 or 10 (7). The 1818 edition of William Henry's El nt f Exp r nt l Ch tr retained the original plate and explanation of Wollaston's scale in the Appendix, but used H = 1 in the text. Henry explained: "To reduce them [Wollaston's weights] to the standard adopted in this work, multiply by 7.5 and divide by 10" (8). Although Andrew Ure's 1821 t n r f Ch tr praised the concept of the scale, he concluded that it "is actually better adapted to the hydrogen unit than to the oxygen" (9). He also observed that such a scale would agree with Davy's system of proportions and Gay Lussac's theory of gaseous combination. Gradually H = 1 became the accepted standard since it avoided most fractional values. By 1830 most textbooks used the hydrogen standard. Other chemical slide rules were also marketed in England. An improved version was published by David B. Reid in Edinburgh in 1826. It was issued with a 40-page pamphlet which discussed the concepts of definite proportions, gave examples for using the rule, and printed a long table of equivalent weights that could be used with the scale. This scale used H = 1 as the standard, but explained that the numbered slide did not start at 1 because the logarithmic distance would require a much longer slide. When hydrogen was used in a calculation, the slide was set t 10H = 10 and then the answer was divided by ten. Similarly, carbon used 2C = 12 (the accepted atomic weight of C at this time was six) and divided the answer by two. The Wollaston rule had also used this technique, but with different numbers. The dimensions of Reid's slide rule are not given in the pamphlet and it is not known if any examples still exist (10). In 1841 William T. Brande, whose textbook used H = 1 as standard, recommended a chemical equivalent slide rule and accompanying table "made by Newman, No. 122 Regent Street, and Palmer, 60 Newgate Street" (11):
h f r f th [W ll t n] n tr nt, h h I r nd t th t d nt, b x d l , b t t f t t n h l n , n t n f v bl l d r th l tr [ ] l n f n b r p n t, nd rr p nd n r f n b r p n th r l t lf p n th r l th pl b t n r l rr n d, h pp t t t r p t v v l nt ... t v d p rpl x n th l th lt pl t f t r , p r t t bl p n t, nt n n p l t f p nd v l nt .
The "Newman" in question was probably John Newman, who was the official instrument maker for the Royal Institution, where Brande was Professor of Chemistry, and the co-inventor of the Newman-Brooke oxyhydrogen blowpipe described by Ross in a recent issue of theBulletin (26) . It is not known if this W ll t n h l l d r l t pp r d n h 8 4 p p r. h slide rule was the same as the Reid instrument or whether any pl t r pr d d n v r l ntr d t r t xt n th f r t h lf f copies still exist. th th nt r . 26 ll. t. Ch . 2 ( 2
British-made slide rules were imported to the United States, but the Beck-Henry slide rule was the first to be manufactured in America. Produced in Albany, NY in 1827, it also used H = 1 as the standard. Fortunately some details of its develop- ment have survived. Joseph Henry (1797-1878) is noted for his contributions to electromagnetism and magnetic induction. He was immortal- ized when the present-thy unit of inductance was named in his honor. As the first Secretary of the Smithsonian Institution, Henry established policies that resulted in the Institution's evolution into its present status as a world-renowned organiza- tion. Though his wide interests encompassed all sciences, he chose, in his own words, to confine his personal research efforts "to a course of study and investigation intermediate to pure Mathematics on the one hand and the more detailed parts of Chemistry on the other" (12). From 1819 to 1822, Henry attended the Albany Academy, where he excelled in mathematics and science. He studied chemistry under T. Romeyn Beck using the 1816 edition of Samuel Parkes' Chemical Catechism, and performed so well that he was hired as Beck's lecture assistant in chemistry for the following academic year (1823-24). He then worked at vari- ous surveying and teaching jobs, including private tutor for the children of Stephen van Rensselaer, the wealthy patron of science. In 1826 Henry returned to the Albany Academy as Professor of Mathematics and Natural Philosophy. During the following six years he conducted many of his electrical experi- ments. Before he began that area of research, however, he and C l b ( 8 8 Lewis C. Beck collaborated in producing their n "Scale of Chemical Equivalents". r n th r ( 82 Mr. ph nr , th n r f r n th Lewis Caleb Beck (1798-1853) graduated from Union Alb n A d (n S r t r f th S th n n In t t t n & College in 1817 and obtained a medical license in 1818. He lf, p bl h d "A S l f Ch l E v l nt ," h h practiced medicine in Schenectady, St. Louis, and Albany n tr t d nd r th d r t n f r. W ll t n, th l br t d before turning to teaching as a career in 1824. He taught En l h Ch t. O r l n rl t th l n th f W ll chemistry and other sciences at Berkshire Medical Institution t n & nt n d th n f r th n d bl th n b r f and Rensselaer Polytechnic Institute and was at Vermont b t n . It l r n tl d . Academy of Medicine in 1827 when work on the Scale of Mr. nr rr n d th d v n n th l d r & f rn h d th Equivalents began. He had undoubtedly met Joseph Henry nt f th M th t l C n tr t n. I rr n d ll b t n while visiting his brother, T. Romeyn Beck, Principal of the rd n t th r t ht, & d th nt r p f r th Albany Academy and Henry's mentor in chemistry. n r v r, r h h f r r r d r t r . Henry may have gotten the idea of making the scale when h l n r v d n C pp r t n d r bl xp n . On he visited John Torrey at West Point in June 1826. He noted r t d ff lt n th f r f th S l , n tt h n in his journal that "Dr. Torrey intends making one of Wallos- th pr nt d p rt t th d r , n h nn r th t th x t r t tons [sic] scales of chemical equivalents & to use Mr. Thomp- h ld b pr rv d n v r p t n f th l d r. h l t son's new attomic [sic] numbers" (13). Beck or Henry may l n th n r v d n b n p p r & p t n b Mr. W l n, l b have seen the newer Reid slide rule mentioned above, since a r, h t d t th nd f r . St ll n f th copy of Reid's Directions pamphlet can be found among r , p n tr l, f nd t b n r t & th r l d d . Henry's surviving papers. The quotations below, however, h r r p bl h d f r t 6 r 8 d z n f th S l , & strongly suggest that Henry and Beck struggled through their b n n d r bl n d nd, pr p r d S nd d t n. In th own design problems. v r l n b t n r ntr d d. t W l n h d, I th n d d It is not clear who suggested the idea of manufacturing the n th n t & r bl d t pl n th r p r n t scale, but Beck, in his autobiography, explained the division of pl t th r . d d n t d v r ll h , nd d, h d n labor and some of the complications (14): d f th r r r d, & th r lt , th t n f th r ll. t. Ch . 2 ( 2 2
l . O t f b t 0, p rh p n t r th n 00 r f t f r . p b th h l l . Y n th r f r f x r pr rd r th xp n & tr bl h h tt nd d th n tr t n f n l . th l , th r n r l ld t n d r bl pr . I r l n h th r th l r ff nt t t xp n , b t On 21 September 1827, Henry wrote Beck (17): th d d n t t th t t nt r nt r l l t n. A t th l I h v nt n d z. t h l d lph nd h lf d z. t Unlike previous chemical slide rules, the Beck-Henry rule r. dl , l l ft n t W b t r nd n th r t r. M th placed a printed "Description and Use" paper pasted on the d r f 2 d z r pl t d nd b f r th r back of the rule. Evidently Henry was overseeing the manu- v rn h d I ll rr t d n th p n. n ll th p r ht [ ] facturing process in Albany. In a letter of 15 April 1827, Beck h h n r n th n n n r h ll b r d. sent Henry a suggested explanation to be put on the back of the scale. He continued (15): Further errors were mentioned in a letter from Henry to John Torrey on 4 October 1827 (18): Y n dd n th r ll tr t n f t t l t n n l . On t I h v n t d. S lph t f t h h ld b 88, I b l v n t d f l h bl d t f r r n t f th rr r n th l . S l. 8 ... t th f pl , & rr t th t , f t n . pp r rd n t h p n h ld h v b n 2 n t d f 2 ll n n r n t th b v " d b rd" r n th r t n th l . S l t n fr r nd t bl ( 2 b t I h h d pt. r th n th n n th t l n ld h v b n b tt r. h rr r h ll b rr t d b f r n r pr n r t n fr The instrument was on the market at least as early as 11 th pl t nd n th n t h ld d v r n r ll September 1827, when Henry wrote a dealer (16): b d t v f rth r n t .
I nd b th b r r Mr. b n n n z n Ch l l . W The completed slide rule measured 18.5 by 2.75 inches and nn t ff rd [t ll] th f r l th n n d ll r & t nt f v Ct the slide scale was graduated from 8 to 330 (The scale began with oxygen, which on the H 1 scale had at the time an accepted atomic weight of eight). Only one of these instru- ments is known to survive, a "second edition", dated 1828, at Transylvania University, Lexington, KY as reported in the article by Bodner mentioned earlier (1). Silliman's American Journal of Science reported both "editions" of the slide rule, noting that it was (19):
... tr n l r nd d b th d pt n f h dr n n t ... r h pp t t th br ht th n r h f ll t d nt f h tr n th ntr . It j tl b rv d th t t f nd d n th t p rt nt f t n th n , n l , th t ll b d n t , h ll , n ht , r lt pl f ht , th t h v th n t nt r t t h th r.
Beck also made passing reference to the scale in his own 1831 text, A Manual of Chemistry (20):
h r t t n b r f h t ll h dr n n t nd th r f r x n 8. h h th t pl , nd h b n d pt d n th l f v l nt n tr t d b r f r nr nd lf.
The absence of further correspondence about the scale in the Henry papers suggests that the project ended in 1828. Both men continued their distinguished careers. Henry was Profes- sor of Natural Philosophy at Princeton from 1832 to 1846 and director of the newly organized Smithsonian Institution from 1846 until his death in 1878. Beck continued to teach chem- ph nr ( 8 8 isiry until his death in 1853, holding professorships at Vermont 28 ll. t. Ch . 2 ( 2
Academy of Medicine, Rutgers, New York University, Mid- alternate substances that would contain the same quantity of dlebury College, Fairfield Medical College, Castleton Medical active ingredient (22). Academy and Albany Medical College. The popularity of the chemical slide rule, at least in con- Yet a second chemical slide rule was also marketed in the junction with the teaching of elementary chemistry, seems to United States. This was announced in Silliman' s Journal in have waned by the second half of the 19th century. This was 1829 (21): certainly implied by the comments of Benjamin Silliman, Jr. on the Beck-Henry scale in his 1874 survey of the history of M r . d & C . f th t pl [M ddl t n, C nn.] h v j t chemistry in America (23): n d th n f t r f W ll t n S l . h n b f r , r t r n th A r n S nt n l, th t f n h d Wh l n Alb n th r. , h [ nr ] d v d nd p bl h d n p n f r n h p f th nd h v v r t n nd th pr v d f r f W ll t n l d n l f h l v l nt , f r t tt pt n b x d, t r n l d , n th ntr . h S l n h h h dr n d pt d th r d x, ntr v n h h 2 n h n l n th, b nd 2 0th n br dth. h r d t n h rdl n n, v n b n , t th pr nt n r t n f h t . d n b h n r , nd x t d th d r f b t nd r h v n v r n l d ... Gr t r h b n t n n However, it was revived again in the period 1910-1950 in the th pl n f rr n nt f th h l b t n . h l nt r form of the "Ashley Chemist's Slide Rule". This was designed b d , t l , nd t ll x d , r rr n d n n d f th for the use of analytical chemists involved in repetitive routine
h " A hl Ch t Sl d l ", r 4
l d , b th lv th n f th t l r pr nt d n l r r analytical procedures and carried the usual C, D, and CI scales t p ... r t t r h b n t n n n lt n th l t t t bl f of a regular slide rule for multiplication, division and recipro- r . nr , h n, nd th r t rr t th rr r f f r r cals, as well as two scales of gauge points, marked by chemical t bl . formulas, corresponding to the molecular weights of the com- h l , th pr v d, d t th t n nd nd r mon reagents and precipitates used in gravimetric and volumet- th p r nt nd n f t. . rr tt ... h pp r t f r ff t n ric analysis (24). A quick survey of laboratory supply catalogs th r d t n , f n v l nd n n nd, nd th nv nt n strongly suggest that the chemical slide rule did not survive f Mr. d ... beyond the 1950s (25). But, if per chance, it did, there is little h r r n n n f t r d n th ntr r l h r , th t doubt that, like the mechanical slide rule in general, it did not n p r th th , th r n h pn , n t l f f n h, n th succeed in weathering the onslaught of the portable electronic n b r f bd v n , r n r f r d t n ... calculator in the 1970s.
To the best of my knowledge no example of the Barratt-Hedge References and Notes slide rule has survived. A novel circular slide rule for equivalents appeared in the A n l d nt: h th r ld l t th n r. W ll . 1828 American edition of J. A. Paris's Pharmacologia. The n n f r br n n th Gr n b l t n r f r n 4, th r d plate on the inside of the front cover of this volume shows a b n r f r n 6, nd th t r l n r f r n , 24, 2 nd 26 t circular logarithmic scale graduated in grains. In the center is h tt nt n, ll f r th nf r t n n th f n l p r r ph f th an inner rotatable disk, 4.25 inch in diameter, marked with the rt l nd n th d nt f t n f nr Syllabus n r f r n 2. names of common medicinals. Labeled the "Medicinal . G. dn r, " h App r t M t r n lv n Dynameter and Scale of Equivalents", this circular slide rule Un v r t ," Bull. His!. Chem., 1990, 8, 22 2 . allowed the user to calculate the quantity of active matter 2. W. . W ll t n, "A S n pt S l f Ch l E v l nt ," contained in any given weight of a medicinal or the weight of Phil. Trans., 1814, 104, 22. S l P. nd , "W ll d ll. t. Ch . 2 ( 2 2
W ll t n. h M n nd h E v l nt ", . Ch . Ed ., 1966, 80 An Ep t f Ch tr r v l n d nt l tl n , v n th 4 , 6 . p l r p ll n . h S ll b l d nt f d th r f . A. Ur , A t n r f Ch tr , . & G. Und r d ... , W ll nr n . rt n t n, A t r fCh tr , M ll n & nd n, 82 , np n t d, nd r " v l nt ". C ., nd n, 62, l. , p. 82 . 4. S : . Gr n , A S n M Ill tr t d l t. . Ib d., p. . Ch tr . [ l.] : Ch l b r t r t 8 0, r M j t 4. Ib d., p. . h ll b r t n l d r b d n C. n St t n r Off , nd n, 66, np n t d ( th ph t I. n C rtl ndt, r n . M d. S . C nt f Alb n , .Y. (Alb n M d. Spr n n, " lt n n W ll t n", Ch . W bl d, 1967, 6 , 2 Ann l , 1864, , 2 2 02. 220 ( th ph t A. S tt, " h At h r , th E p l . Ib d., p. 8 . h xpl n t n n th b f th l f r n t th W r f t nd r t p th ", . Ch . t d n t nt r t n n ld, f r n 2, pp. 4 nd S ., 1917, 6 , 288 . p rt ll n f r n , p. 24 2 . . An n , E rl S n t rv rd, rv rd Un v r t 6. Ib d., p. 6. r , C br d , MA, 6 , p. 6 An th r d r pt n, th . Ib d., p. . ph t r ph, n I. . C h n, S E rl l f A r n S 8. Ib d., p. . n , rv rd Un v r t r , C br d , MA, 0, pp. 8 , 66, . [ . S ll n], "Int ll n nd M ll n ," A . . S ., . , 2. 1828, 4, 202 20 1830, 8, 8 . h t t n fr th 8 0 6. W. nr , h El nt f Exp r nt l Ch tr , t t n. W b t r, h l d lph , A, 8 , App nd x p. xv lxv , l t I 20. . C. , A M n l f Ch tr , W b t r nd S nn r , W. nr , h El nt fExp r nt l Ch tr , b rt lv r, Alb n , Y, 8 , p. 4. h l d lph , A, 8 , l. , App nd x p. v nd l. 2, l t I 2 . [ . &In n], "Int ll n nd M ll n ," A . . S ., . G rh , h El nt f Ch l S n , C n nd 1829, 6, 2. ll rd, t n, MA, 8 , l. , pp. 4 th l t r d 42 22. . r , h r l , E. n , C ll n & C ..., . C tt n , An Intr d t n t Ch tr , Ch rl E r, t n, MA, Y r , Y, 828, n d fr nt v r nd pp. 24 244. h d f 822, pp. 4 nd l t W. . M n v n, Exp t n f th At b t n n l r d d th h nd ppl d t r l r . h r f Ch tr , Gr tt n nd n , Y r , Y, 8 , pp. 2 . . S ll n, A r n C ntr b t n t Ch tr , C ll n , 62 . h W ll t n l d r l l nt n d n th r t h nd h l d lph , A, 8 4, p. . A r n d t n f M h l r d b Ch l M n p l 24. A br f d r pt n f th A hl l d r l n b f nd n . t n, M. r d , Ch l M n p l t n, C r nd , h l E. h p n, A M n l f th Sl d l : It t r , r n pl nd d lph , A, 8 , pp. 8 . Op r t n, n tr nd, Y r , Y, 0, pp. 2 2 2. . . h n, h t r f Ch tr , nr C lb nd 2 . h , f r x pl , th 4, 2 nd t l f r th h rd ntl , nd n, 8 , p. 2 . E. . S r nt C . f Ch ll rr d th A hl h l l d 8. W. nr , El nt f Exp r nt l Ch tr , b rt r l , b t t n l n r ff r d n th 6 t l . It l l t d lv r, h l d lph , A, 8 , l. 2, p.420. n th t l f th S nt f M t r l C . f tt b r h, th . f r n , np n t d, nd r " v l nt ". 28 t l f th W l n And r n C . f Ch , nd th 6 0. . d, r t n f r U n th I pr v d Sl d n S l f t l f th E r nd A nd C . f Y r , b t t n Ch l E v l nt th h rt Expl n t n f th tr n f fr th 2 E r nd A nd t l nd th 6 t l f r f n t r p rt n , M l hl n nd St rt, Ed nb r h, 8 , 40 h r S nt f f tt b r h. h 6 E r nd A nd t l pp. ( r t d t n 826, Ed nb r h, p bl h r n n n. h l rr d th " tl r h l l d r l ". p phl t n l d d rt II f d El nt f r t l 26. S. , "Unp bl h d tt r f r d nd Oth r t Ch tr ..., M l hl n nd St rt, Ed nb r h, 8 0, pp. 408 442. Ed rd n l Cl r ", ll. t. Ch ., 1991, , 86. . W. r nd , A M n l f Ch tr , hn W. r r, nd n, 84 , l. I, p. 2 . 2. . n ld, h p r f ph nr , S th n n In t t t n r , W h n t n, C, 2, l. , p. 4 . nr William D. Williams is Professor of Chemistry at Harding th r t v t n h tr r n r. In 8 2 h ll b r t d th University, Box 602, Searcy, AR 72149-0001. A frequent . . nd C. n p bl l t r r n h tr contributor to the Bulletin, he collects and studies early t Alb n , b t h ntr b t n ph z d ph h l American chemistry texts. t ht th h tr . In 8 h t ht hn rr r h tr r t r n t n h l rr n E r p . h t n l Un n C t l nt n n rr n l t n , t n ph NOTICE: If any of our readers know of other locations of nr th th r f S ll b f C r f t r n Ch tr additional examples of any of the chemical slide rules men- (40pp., n d t , n pl , n p bl h r . h pr nt t ll th tioned in this article, both the author and the editor would r f W ll nr . A p r n f th S ll b th nr appreciate hearing from you.