Readings are taken at regular intervals of the amount of water passing through in one minute. The flow of water through the test piece diminishes as the test progresses and readings are accordingly taken at longer intervals until the flow of water becomes

constant.

In testing the 2-inch cubes for absorption they are weighed after being thoroughly dried in a gas oven at 100° C. They are then placed in water for twenty-four hours and again weighed. The difference in weight is the absorption.

Forms.-The forms used for recording results of tests give the usual information concerning register number, consistency, etc., also the kind of waterproofing used, the thickness of the specimen, the weight of water absorbed, and the weight of water passing.

CHEMICAL SECTION.

OUTLINE OF INVESTIGATIONS.

The chemical laboratory is equipped with every facility for making the analyses which are required in the course of the investigations of structural materials. In addition to its work in connection with the structural-materials division the laboratory has been making a large number of analyses of cement-making materials (limestone, shales, etc.), for the Reclamation Service.

An annex to the main laboratory communicates with a combustion room, a sampling and storage room, a balance room, and an office. The equipment is very complete and comprises analytic balances, pulp balance, copper still, electric stirring apparatus, gas retainer, carbon dioxide apparatus, oxyhydrogen blast lamps, muffles, and an ample supply of platinum, nickel, and glassware.

ANALYSES OF CONSTITUENT MATERIALS.

CEMENT.

In the analysis of cement the methods recommended by the committee on uniformity in the analysis of materials for the Portland cement industry of the New York section of the Society for Chemical Industry are used, with the following exceptions: In the analysis of cements the silica is not purified by treating with HFl and H2SO. The precipitated iron and aluminum hydrates are dissolved in dilute HNO, instead of in dilute HCl; the ignited CaO is also precipitated from a HNO, solution the second time. Lastly, the SiO, is not determined in the ignited Fe2O, and Al,O,.

SILT AND OTHER MATERIALS.

METHODS.

The methods used in the analysis of silt and other materials are those described in Bulletin No. 305 of the United States Geological

Survey, on the analysis of silicate and carbonate rocks, prepared by Dr. W. F. Hillebrand, with the following exceptions:

Moisture at 100° C.-A 1-gram sample of the silt is weighed out upon a small watch glass. It is heated for two hours at 105° C. in an air oven and is weighed after being allowed to cool in a desiccator. The loss in weight is checked by another heating for one hour in the oven.

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Silica. SiO, is usually not treated with HFl and H2SO to determine the Fe,O, and Al,O, which is invariably present; at the same time the Fe,O, and Al,O, are not evaporated with H2SO, after the bisulphate fusion to determine the SiO, present in them. In the greater number of cases these two errors about counterbalance one another. The ferric oxide (Fe,O,) and alumina (Al,O,) are precipitated with ammonia, washed with hot water containing 20 grams ammonium nitrate per liter, dissolved in nitric acid, and reprecipitated. The Fe,O, is reduced by zinc and not by hydrogen sulphide.

Manganese oxide.-MnO is determined by precipitating the hydrated MnO, with bromine water in the filtrate from the iron and alumina, filtering, igniting, and weighing as Mn,O1.

Total moisture.-One gram of the material is weighed out into a porcelain boat and placed in a piece of hard-glass combustion tube, which is contained in a combustion furnace of the ordinary type. This is preceded by a U-tube, one arm of which is filled with CaCl, and the other with soda lime; this is preceded by a bubble tube filled with H,SO1, and is followed by a U-tube filled with CaCl2, which is followed by another of the same, serving as a safety tube. About five of the burners are lighted under the boat and the total H2O driven out of the material. The H2O is drawn through the tube by a current of air and is caught in the U-tube containing CaCl,. The increase in weight of this gives the total H,O-from which is subtracted the moisture-giving the H2O above 100°. Necessarily the combustion tube must be heated and the whole train freed in this way from H2O before the boat with the material has been inserted. Carbon in organic matter.-One gram of the material is placed in the small beaker and 60 cubic centimeters H,O and 10 cubic centimeters HCl added and warmed. The mixture is then filtered through a perforated platinum boat containing a mat of ignited asbestos. The boat is then dried at 100° and placed in a combustion tube contained in a 16-burner combustion furnace. This is preceded by a U-tube, one arm of which is filled with CaCl, and the other with soda lime, which is preceded by an absorption bulb filled with 1.20 specific gravity KOH and this preceded by a second combustion tube contained in a second furnace. This second tube can be connected either with a U-tube filled with CaCl, and soda lime, preceded by a KOH bulb filled with 1.20 specific gravity KOH, or with an oxygen

holder. The combustion tube in the first furnace is filled as follows: About 3 inches from one end (which becomes the posterior end in the furnace) is placed a plug of asbestos followed by 5 or 6 inches of coarse granulated CuO, then by 3 inches of ignited lead chromate and a second plug of asbestos, and the whole finally followed by a roll of silver foil about 11⁄2 inches long. The second tube is filled in the same way except that about twice as much CuO is used and the silver foil is omitted. After the first tube there is placed a bubble tube filled with acid (AgSO,) to catch any HCl not washed out of the boat. This is followed by a U-tube filled with CaCl2, then an absorption bulb filled with 1.20 specific gravity KOH, to which is connected a CaCl, drying tube, and the whole is followed by a guard U-tube filled with CaCl2. With all the burners in the furnace turned on full except the one at each end, a current of oxygen is drawn through the train for twenty minutes, then air is drawn through for ten minutes. The absorption KOH bulb following the first furnace with its connected CaCl, tube is then weighed. The increase in weight is equal to the CO, and this multiplied by 0.2727 gives C.

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Necessarily, before placing the boat in the furnace, oxygen must be passed through it and all C burned completely out of it, a condition which is attained when there is no further increase in the weight of the absorption bulb.

SUMMARY.

The above methods apply equally well to shales, to clays, and to all high SiO, rock-also to limestone, but in this case only about 1 or 2 grams of the mixed carbonate of potassium and sodium are needed in the fusion.

Form R is used for recording the analyses.

ANALYSIS OF STEEL.

All the steel used in the reinforced beams is analyzed. The percentages of carbon, phosphorus, and sulphur are determined by the usual methods and are recorded.

Carbon is determined by solution of steel in potassium cupricchloride filtration and combustion of the residue. (Blair's "The Chemical Analysis of Iron," 6th ed., pp. 156-166.)

Phosphorus is determined by the volumetric method proposed by the subcommittee on methods of the International Steel Standard Committee of the United States. (Blair, pp. 92–104.)

Sulphur is determined by evolution as hydrogen sulphide and absorption in ammoniacal solution of hydrogen peroxide. (Blair, pp. 60-65.)

INVESTIGATIONS OF COLUMNS AND FLOOR SLABS.

A comprehensive series of tests is being inaugurated to investigate the properties of both plain and reinforced concrete columns ranging in length from 10 to 30 feet and in section from 8 to 12 inches.

A series of tests is being put into execution to investigate the properties of concrete slabs reenforced with steel of 10-foot span. The column tests have been delayed awaiting the arrival of the 600,000-pound testing machine, the installation of which will make it possible to proceed.

THE EFFECT OF ELECTROLYSIS AND SEA WATER ON CEMENT MORTARS AND CONCRETES.

In connection with the work of the laboratory at Norfolk, Va., there is being conducted a series of investigations covering (1) the effect of electrolysis on cement mortars and concretes, and (2) the effect of sea water on these materials. In this latter series of experiments test pieces are being made with sea water and immersed in sea water, made with fresh water and immersed in sea water, and a parallel series made with and immersed in fresh water. A series of parallel experiments will be carried on in St. Louis as to the effect of electrolysis on cement mortars and concretes. The cages in which these test pieces are stored are located at the end of what is known as the commercial pier, which extends about 1,500 feet from the shore, near the grounds of the Jamestown Exposition. The use of this pier has been obtained through the courtesy of the local authorities.

PROGRESS OF THE WORK.

PRELIMINARY WORK.

The appropriation for the first year's work amounted to $12,500, of which $5,000 was carried by the general deficiency bill and was available until June 30, 1905, and the balance, $7,500, was available until June 30, 1906.

The appropriation was made for the purpose of continuing the investigations started during the period of the Louisiana Purchase Exposition, and it was expected that light, heat, and power would be furnished by the fuel-testing division, which would considerably increase the funds available for actual testing work. During that year the work consisted principally of the investigations of the constituent materials of cement mortars and concretes, the work being carried on in the cement building now used by the constituent-materials section.

Late in the fall of 1905 the metal pavilion was occupied and was used for several months as a temporary storage house for the materials used in the investigations then pending. The funds for the work, however, were so small that it was necessary to reduce the force of men employed on this work in the spring of 1906, which brought it practically to a standstill until the new appropriation of $100,000 became available for the fiscal year beginning July 1, 1906. After this date the work was again taken up and greatly extended; the beam, building-block, and computing sections and a chemical laboratory were organized,, and new equipment was purchased and installed.

PRESENT WORK.

During the fiscal year 1905-6 the work at the laboratories was greatly hampered by the removal of the buildings which formed a part of the Louisiana Purchase Exposition, which work extended through 1906 and well into 1907, and rendered it difficult to repair the buildings and to install the apparatus required in making the tests. This necessary work, however, was accomplished during the summer and fall of 1906, so that the work of the new divisions was well under way early in 1907.

During the fall of 1906 and the first half of 1907 many test pieces have been made and tested. Those made prior to July, 1907, aggregate 35,200, while the number of tests and determinations which have been made amount to 35,500.

The approximate number of test specimens made and tested is divided among the various sections as follows:

Constituent-materials section. In the constituent-materials section there have been made 5,750 transverse specimens 1 by 1 by 13 inches; 8,700 two-inch cubes; 12,550 tensile briquets of 1-inch cross section; 870 cylinders 8 inches in diameter and 16 inches long; and 710 six-inch cubes. Of these there have been tested 3,650 transverse test pieces; 6,740 two-inch cubes, 540 six-inch cubes; 9,750 tensile briquets, and 600 cylinders. In addition to the above about 10,000 physical determinations of specific gravity, time of setting soundness, mechanical analysis, etc., have been made.