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 Fe,O, 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 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. Silica. SiO, is usually not treated with HFl and H,SO, 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,SO,, and is followed by a U-tube filled with CaCl,, 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 H2O-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 H.O 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 HC 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 1 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 CaCl,, 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 CaCl,. 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. 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. |