John T. Stock University of Connecticut Storrs, 06268
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The biographies of James Curtis Booth (Fig. 1) indicate that he was remarkable both as a man and as a He graduated from the University of Pennsylvania in 1829, then went to Germany a few years later. Here he studied analytical chemistry with Wohler. Booth wished to continue his studies with Berzelius, the great Swedish analytical chemist. Wohler's letter of recommendation to Berzelius describes Booth as having an innate love for chemistrv. "He has a right eood head. hut I & not think he will be prdductive or origin& new or broad ideas. He is very industrious, scrupulously conscientious, and accurate." Wohler's assessment was a eood one. Booth did not discover a new element or propose a new theory. Instead he became a great teacher of practical chemistry and an outstanding professional scientist. Berzelius replied that he was too old to take on further students. Accordingly, Booth continued his studies in Berlin and in Vienna, visited various chemical plants, then returned to Philadelphia towards the end of 1835 or early in 1836. Here he started a teaching laboratory that provided excellent instruction in practical chemistry. Many of his students became successful professional chemists; some occupied professorial chairs. In addition to the running of this laboratory, Booth taught chemistry in the Franklin Institute and in the Philadelphia High School. From 1851 to 1855, he held the Chair of Chemistry Applied to the Arts in the University of Pennsylvania. The exercise of first-class teachine ahilitv was onlv one aspect of Booth's talents. He was an energetir and reso~~rceful rmsultinr chemist with a wrll-deserwd re~utationfor skill and accur&y. His knowledge of m i n e r a l ~ ~ j f i t t him e d to become a memher of the first geological survey of Pennsylvania and then State Geologist of Delaware. However, Booth's deepest love was of chemistry, especially of metals. In 1849, he was appointed Melter and Refiner to the Philadelphia Mint and held this position almost up to his death. This appointment was no sinecure, because i t virtually coincided with the discovery of gold in California. Under Booth's supervision, the
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operations expanded from those of a laboratory to those of a factory. Booth was an active memher of many learned and professional societies, including the American Chemical Society. He was its President in 1883 and 1884. He died on May 21, 1888. A few years ago, Dr. H. R. Roberts, Director of the Philadelphia Academy of Natural Sciences, allowed me to inspect the balance shown in Figure 2. It is marked "Balance of James Curtis Booth" and has a brown cloth cover hut no case. Although there are independently adjustable leveling screws, there is neither spirit level or plumbline. However, a circular boss to the right of the center column may have once been the site of a level. Two cheesehead screws pass through the castiron base and secure the massive bronzed column. A steel cylinder p r o j ~ clrum f ~ the top ofthe column. This rylinrler is sl~fterl1') ~rrommodatethe beam and it- to11is hi~hl\.finished to form the planes upon which the beam s&ngs. The har-type beam carries three small steel knives. Those near the ends of the beam are 9 in. apart and are only '18 in. long. A 4%-in. long steel pointer projects upwards from the center of the beam and moves across a tiny circular scale. Only three lines, approximately 56 in. apart, are marked on this scale. Two pushbutton keys at the front of the base control the action of the balance. Depression of the left-hand key allows the balance to oscillate. Pressure on the right-hand key frees the beam but keeps the pans arrested.
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Figure 1. James Curtis Booth (1810-1888).
Dubois, P., Proc. Arner. Philosophical Soc., 25,204 (1888). 'Smith, E. F., "James Curtis Booth, Chemist," (brochure based on account given to the Historical Section of the American Chemical Society, Sept. 9,1922). :'Smith, E. F., d. CHEM. EDUC., 20,315 (1943). Volume 53,Number 8. August 1976 / 497
Flgurc 3 Closeup of end of beam
Normally, the beam is supported clear of the cylinder top by a small conical pin on the upper side of each of the wings that extend horizontally from the column. A closeup view of the rieht-hand ends of beam and wine is shown in Fieure 3. The din mates with a conical depression in the underside of the beam. De~ressionof either of the kevs causes the cvlinder to rise, to make contact with the cente;knife, and toiift the beam clear of the pins. A circular plate, formed on the extremity of each wing, has a diamond-shaped opening. This engages the chamfered sides of the pan hanger when the balance is arrested and this locates each end plane with respect to its knife. Heavily blackened when examined, the pans are only 1% in. in diameter and may he of silver-plated brass. Twin wires, not unlike those used in a modern balance, support each pan. These wires merge into one and are joined to the hanger by means of a tiny universal joint as shown in Figure 4. The chamfered sides of the hanger are shown more clearly here. Two screws secure the bridging bar to the hanger. Polished on the underside, this bar forms the plane that makes contact with the knife a t this end of the beam. Normally, a button beneath each pan lifts it slightly, so that the end planes are held clear of their knives. These buttons sink when the lefthand key is depressed. 'Stork. J. T.. "Development of the Chemical Balance," British Tnforrnatlon Services, New York, 1969, p. 22. t
498 / Journal of Chemical Education
There is no obvious provision for adjusting either the zero or the sensitivity of the balance. However, when leveled, the tip of the pointer was found to rest quite close to the center line of the scale. The placing of a 5-mg weight on the right-hand pan caused the pointer t o move to the right line of the scale. A reasonable estimate is that, if shielded from drafts, the halance might be capable of making a weighing good to approximately 1 mg. This balance is an extremely interesting instrument. Its design is a mixture of naivete and ingenuity. In particular, the "diamond hole and chamfered hanger" is a clever Figure 4. Hanger and universal joint. method of orovidine for the location of t i e end pLnes with respect to their knives. This advanced feature, together with the-use of the knife-and-plane system for all three main pivots, is strangely at odds with the ~ d i m e n t a r ybar-type beam and the lack of sensitivity control. My guess is that the unknown maker was an excellent workman, hut did not specialize in weighing devices. Anomalies in balance construction were certainly not confined to the budding scientific instruments programs of 19th-century U.S.A. For example, a balance (also by an unknown maker) in the Museum of the History of Science a t Oxford, England, has a light, triangulated beam, the steel knife of which turns on planes of quartz or glass. These desirable features are offset by the use of a quite rudimentary form of swan-neck end hearing.4 Bearings of this form are of little use in balances that are intended for work of high precision.
Acknowledgment -
This work was carried out with the partial support of the University of Connecticut Research Foundation.
