Popular Science Monthly/Volume 79/September 1911/The Bureau of Standards
|THE BUREAU OF STANDARDS|
By Professor HENRY S. CARHART
UNIVERSITY OF MICHIGAN
THE scientific bureaus of the government in Washington are conducting investigations on a scale and of a degree of merit not fully appreciated by the public because so little is known about them. The Imperial Institution known as the Reichsanstalt in Charlottenburg, a suburb of Berlin, has acquired international fame; and the National Physical Laboratory at Teddington in the environs of London is nearly as famous as a government institution of research.
In no way inferior to these is our own Bureau of Standards, situated out on the hills in Washington toward Chevy Chase. It has just completed its tenth year. Its activities in the interest of standards of measurement and of excellence entitle it to as high a position in popular favor as it already enjoys in the esteem of scientific workers and of those applying scientific data to practical ends.
The two prime functions of the bureau are to serve the government and the larger clientele of manufacturers and ultimate consumers. To which beneficiary precedence should be given is a question; happily whatever serves the one serves also the other.
The bureau is by law the custodian of all physical standards, and is authorized by the act creating it to exercise such functions as are necessary for their construction, comparison, maintenance and dissemination. In addition to these duties is the highly important one of defining standards of excellence for manufactured articles and materials of construction of which the departments of the government are large consumers.The division of electricity has made its full quota of contributions to the fixing of standards of electrical measurement in comparison with similar institutions of other governments. In recognition of this fact,
A View of the Present Buildings.
one delegate each from the Physikalisch-Technische Reichsanstalt of Germany, the National Physical Laboratory of England, and the Laboratoire Central d'Electricité of France came to Washington in April, 1910, and in cooperation with representatives of the Bureau of Standards carried out an extended series of experiments on the three fundamental standards of resistance, current and electromotive force. As one result of this cooperative work an agreement has been reached with respect to the value to be assigned to the Weston normal cell; it has been accepted by the International Committee on Electrical Units and Standards, and is therefore universal. The difficulties in the way of the complete unification of international electrical standards have now practically all been resolved.
In the other field of defining and maintaining standards of excellence, this division has been no less successful. The incandescent lamp industry is a shining example. Before the establishment of the bureau, the navy department was under the necessity of seeking the services of the German Reichsanstalt for the purpose of standardizing lamps for use in the naval service. At that time the different departments of the government purchased lamps on independent contracts, while purchasing agents had no scientific means of justifying awards. Hence the intrusion of political influence with the object of securing contracts for friends or constituents. Criticism of such action was not justified so long as the government was without the means of defining and defending standards of excellence to which the articles purchased should conform.
It has happened in the past that awards have been held up by congressional influence, and the awards have been modified to include the product of small manufacturers, who claimed to make lamps in every way the equal of those made by the large manufacturers of wider experience and technical skill. Subsequent tests at the bureau showed that some of these added awards were filled by lamps which did not meet the requirements of the contract, and they were rejected.
At the present time the general supply committee awards contracts for all departments of the government and the Secretary of the Treasury signs them. This year the contracts for the list of articles for which the committee has made awards aggregate about nine million dollars. All departments are furnished with lamps purchased under uniform specifications, and tested the year round by the bureau. Moreover, the government now has the advantage of million rates instead of ihe higher prices attaching to contracts for smaller numbers.The lamp contract of the government calls for about one per cent, of the incandescent lamps made in this country. The other 99 per cent, are sold to the general public. If the government took the best million made, while lamps of lower efficiency and shorter life were sold to the public, the government would be the gainer at the expense of other
consumers. But the fact is that the check held by means of the life and efficiency tests made at the bureau, and by the work of inspectors who visit lamp factories with bureau standards and instruments, has had the effect of gradually raising the quality of all lamps made; so that the consumer at large has profited equally with the government in the improvement of the lamp product. The bureau cooperates with the technical staff of the best manufacturers, large and small, and is in this way influential in raising the standard of excellence. Since the lamp trust fixes and maintains prices, the only advantage the government gains by competition is the competition in excellence. A consignment of 50,000 lamps has just been rejected because they fell ten per cent, below the guaranteed life.
The work of other divisions of the bureau, while not appealing perhaps so directly to popular interest, are of no less value to the public weal. For example, the bureau is the legal custodian of the international primary standards of length and mass in the form of the national prototype meter and kilogram, by which the yard and the pound are respectively defined. From these and by methods and instruments of the highest precision our customary commercial and scientific standards are derived. In fact the integrity of our gold and silver coinage can be maintained only by occasional refined checks against the ultimate standard of mass in the vaults of the bureau. The prototype standards are composed of incorrodible metals in alloy; no standard made of brass, for example, could be trusted to withstand the effect of oxidation during a long period of years, though happily a recent test at the bureau of the celebrated brass "troy pound of the mint" shows that it has not changed in the 83 years since it was received from England by more than 0.005 grain.
The Coast and Geodetic Survey is engaged in extending its measurements across the continent by means of triangulation. Formerly the survey had only about twelve base lines, each from five to ten miles in length, extending 3,000 miles from the Atlantic to the Pacific. These base lines had been measured with the greatest precision and at night to avoid temperature changes. The department is at present engaged in filling in intermediate base lines, which can now be measured readily by means of modern steel and "invar" tapes to one part in a million. Moreover, the work can be done daytimes and with steel tapes under known tension. The bureau compares these tapes, under the same tension and at the temperature of melting ice, with the primary standard of length, the national prototype meter. Thus it comes to pass that our continental surveys from Maine to California, and even to Alaska, are on the same basis of measurement as those made in other parts of the civilized world.
The bureau is charged with the duty of furnishing to the several states commercial standards of weights and measures in common use. It offers its services free to the state authorities and invites to a conference
every year state and city sealers of weights and measures for the purpose of discussing the best methods of securing the use of legal measures of all sorts, and the prevention of frauds by the commercial use of fraudulent weights. The frauds committed against the government by the sugar refiners were nothing in comparison with those perpetrated on the people by short weight in small commercial transactions.
The bureau has in the field a force of inspectors, cooperating with the state authorities in the detection of fraudulent weights and of short liquid and dry measures. Some of these are used innocently, but many show unmistakable fraudulent intent. The fifth annual conference on weights and measures adopted a resolution favoring legislation requiring that all containers be plainly marked to indicate their net content; also that authority be given to the Bureau of Standards by congress to pass on types of weighing and measuring devices used in trade.
The division of heat has had a particularly arduous task to perform. In contrast to the certainty and permanency of standards of length and mass, and of electrical quantities, there have been great discrepancies in temperature scales and the thermal constants depending on them. The standards used by different makers of thermometers were not in agreement with one another, nor did they agree with the accepted gas scale. There were marked differences even between the usual limits of freezing and boiling, or 0° and 100° C. When the work on thermometry was undertaken, a large per cent, of American-made thermometers for temperatures as high as 400° to 500° C. were subject to changes of 30° or 40° when exposed to the high temperatures they were designed to measure. Further, the average clinical thermometers, used so extensively by physicians, were subject to errors exceeding the limit of tolerance. At least 30 to 40 per cent, of the clinical thermometers on the market at the beginning of the work would have failed to pass the requisite test; to-day only about five per cent. fail. The bureau now tests many thousands of them annually. So great has been the improvement in American-made thermometers that the German makers are complaining more and more of the loss of American trade in thermometers; and some familiar types of mercury-in-glass thermometers are no longer classed as instruments of precision.
Not only has the bureau authoritatively fixed the scale ranging from 0° to 500° C, but it has met a demand for the accurate measurement of very high temperatures by investigating optical and radiation pyrometers, in which the temperature of an incandescent body is measured by the amount of light or heat emitted. The intensity of red light emitted by a body at 1500° C. is over 130 times as great as at 1000° C; and at 2000° C. it is more than 2100 times as great. Hence the possibility of a rough estimate of the temperature of hot bodies in the arts by an experienced eye. The temperature scale of the bureau is now reproducible to about 1° at 1000° C. and to about 10° at 2000° C.
It should not be supposed that the constant efforts for higher accuracy are made to satisfy the dreams of the pure scientist; they are demanded by the requirements of technical tests and commercial processes. The character of some products is materially affected by a variation of 20° in the very high temperatures employed in their manufacture, and an accuracy of about 10° is required. To meet this demand there must be the exercise of man}*-precautions and the elimination of many sources of error.
The importance of great accuracy is well illustrated by a test which the bureau was called on to make in a dispute between a purchaser and a seller of coal, in a case where the contract was based on the heat value of the coal, with a penalty clause for any deficiency in the heat value, and a premium for any excess above the stipulated one. A difference of about 0.05° was found between the thermometers used by the two parties. While this difference was small, it was sufficient to bring the parties into agreement, and to make a difference of some $25,000 a year in the money paid for the coal.
The division of optics has been engaged in many investigations of moment, but none of more practical value than the improvements in the application of polarized light to the testing of sugar solutions by means of the polariscope. Plane polarized light differs from common light in having all its vibrations reduced to a single plane. The optical property of a sugar solution utilized to determine the amount of sugar present is its property of rotating the plane of polarization when the polarized light passes through it. The degree of rotation determines the per cent, of sugar present.
The bureau is able to make immediate application of its research work in this field, thus directing public attention to the results attained. As a result of the polariscopic tests of imported sugars at the bureau, the differences in the findings at the five principal sugar ports of entry have been reduced to 0.2 per cent. The importance of this work grows out of the fact that it increases the accuracy of the tests made on dutiable sugars and rigidly defines the scientific basis on which the revenues from them are collected.
The division of chemistry is in a large way auxiliary to all other divisions and cooperates with them in giving such service as chemistry alone can offer. It has been indispensable in the work of the division of electricity; it has prepared materials in the purest form for setting up Weston normal cells as standards of electromotive force, and for use in the silver voltameter for the international unit of electric current.
Much of the labor in testing supplies offered by the bidders under the new system of purchase by the General Supply Committee devolves on this division. The analyses of writing and printing inks, paper, and mucilage alone amount to an annual total of about 2,000 samples. These chemical analyses and conjoint physical tests furnish a scientific basis for more definite specifications for future purchases.
A demand has developed for certified samples of iron and steel of definite composition; also for samples of sugar of the highest purity. Many hundreds of these are sent out annually. They are highly important
to encourage the growing tendency to apply pure science to commercial processes in place of haphazard traditional methods.
The engineering section of the bureau is one of the later ones established. It has already much more than justified itself. In addition to the work in Washington, designed to secure fundamental data for engineers, it carries on investigations at Pittsburgh in the building turned over by the Geological Survey by direction of the last congress. The work in Pittsburgh under the old organization formed a part of the technological division of the survey.
The engineering division is performing an important service for the government in testing all cement made by the Atlas Cement Company for the Panama Canal. The company furnishes cement at the rate of 6,000 barrels a day. Inspectors are stationed at the works, and the bureau maintains there a well-equipped laboratory.
The testing of all paper purchased for the Government Printing Office falls within this division, in cooperation with the division of chemistry. Formerly bids were received on specifications, the lowest bid was accepted, and then the successful bidder proceeded to furnish the cheapest paper he could get accepted without further regard to the specifications. The results were that the best paper manufacturers refused to bid because they could not afford to sacrifice their reputation, and the government was defrauded. On one occasion the award for paper for the Bulletin of the bureau was made on specifications calling for paper of definite weight and half rags. When the paper had been made and submitted to the Printing Office, the analysis of the bureau showed that it contained no rags whatever, but only wood pulp.
At present print papers are bought on rigid specifications, and samples of all shipments are analyzed at the bureau. The fraud perpetrated on the government in the matter of print paper of all grades has now been eliminated.
Printing inks are purchased at present in the same manner, and the assistance of the bureau has saved the government in this particular item enough to cover about half the cost of the inks. The same system has stopped the graft by commissions once practised in the Bureau of Engraving and Printing by a trusted foreman. The price was very high on account of the generous commission allowed the foreman. Preferences for a particular make of ink or other commodity must now be supported by something more than the dictum of an old employee.
The engineering division does not confine its activities to the direct service of the government. Its aim is also to furnish scientific and physical data which lie at the foundation of engineering practise and design. It is now engaged in the actual measurement of the stresses producing compressions and elongations in the steel members of bridges and other structures after erection, as compared with those calculated by the designers. The results of such a comparison should be of eminent service to engineers and makers of structural steel, as well as to the government in the design and construction of its battleships. The largest testing machine, now in process of erection at the bureau at a cost of $150,000, is to be a marvel of precision. It will apply a maximum force of compression of 2,300,000 pounds, and will measure it with an accuracy of two pounds.This brief survey of the activities of the Bureau of Standards is
necessarily incomplete. It touches the high spots and refers only to matters likely to be of most popular interest. The work is progressing in all divisions with a vigor and comprehensiveness that promise even better results for the near future. The last congress made an appropriation of $200,000 for the erection of an additional building for the exclusive use of the division of electricity. The pay roll of the bureau includes about 280 names, and after July first it will be increased to something over 300. The additional assistants will enable several divisions to push forward work of great practical significance.
It would be an injustice not to say that the success of the bureau has been due in no small degree to the continuous service in their respective positions of Dr. S. W. Stratton as director, Dr. Edward B. Rosa as chief physicist, and Mr. L. A. Fisher and Mr. Charles W. Waidner as associate physicists at the head, respectively, of the divisions of weights and measures and of heat.
The scientific conclusions and data secured are published in a series of bulletins, which have now reached the seventh volume and which bear witness to the activity of this branch of the public service. In addition to the bulletins, circulars on important practical problems are issued from time to time; these are sent freely to persons and firms likely to need them in their professional practise or in manufacture. It is a matter worthy of the highest praise that party politics has never had any place whatever in the support or work of the Bureau of Standards.