An analytical method of ²²⁶Ra in hot spring water was studied. ²²⁶Ra in 2L of water was co-precipitated with barium sulphate by adding sulphate ions in boiling water. Barium and radium sulphate were converted to carbonate by melting with a mixture of Na₂CO₃ and K₂CO₃. The barium and radium carbonate dissolved in diluted hydrochloric acid were absorbed on a cation exchange column (Amberlite IR-120) and ²²⁶Ra was eluted with 2N ammonium formate solution. The fraction of ²²⁶Ra was evaporated in a stainless steel planset and its radioactivity was counted with proportional gas flow counter. The limit of determination was 1.0 μμci/L.

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Diffusion of filth and backward run of sea in the Naka river, tidal stream of moderate mixing type river, were investigated at the high tide. The results obtained were as follows. 1. Backward run of sea in the river is fixed independently of the sea level. 2. In the tidal river of the moderate mixing type at the high tide is more than that at mean sea level, however the distance of the backward run is almost changeless. 3. The diffusion of filth on side of the bank where a polluted tributary joins the main stream is less than that in the central area of the main stream. Therefore, on side of the band at downstream from junction, the stream may be easy to be polluted successively.

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It was found that the sodium salicylic acid method is more excellent in point of reproducibility and simplicity than the other methods for the determination of nitrate nitrogen in water. Furthermore, the authors improved the precise conditions of procedures of the method, for example, the prevention of the interference of chloride ion and nitrite ion. The interference by chloride ion was prevented by the addition of the excess quantity of sodium chloride and that by nitrite nitrogen was also prevented by the addition of ammonium sulfamate. It was also ascertained that the method is not interfered by 50 ppm of ferrous or ferric ion, 2000 ppm of calcium and magnesium salts, 250 ppm of ammonia nitrogen and 500 ppm of free chlorine. The details of the procedure are as follows. Take V ml of the test solution containing 2∼20 μg of nitrate nitrogen and 2 ml of the standard solution, in which 20 μg of nitrate nitrogen are contained, in the 100 ml beaker respectively. To each solution add 1 ml of sodium salicylic acid-sodium hydroxide solution, which is prepared by dissolving 1 g of sodium salicylic acid in 100 ml of 0.01 N sodium hydroxide solution, 1 ml of ammonium sulfamate aqueous solution (0.1→100) and 1 ml of sodium chloride aqueous solution (0.2→100), then evaporate the solution to dryness on the water bath. After cooling to room temperature, and 2 ml of concentrated sulfuric acid, agitate gently sometimes and allow to stand for ten∼twenty minutes. When the large quantity of the residue remains by evaporation, it might be better that the sulfuric acid solution is heated on the water bath for ten∼twenty minutes. The absorbance is not influenced by heating. After adding carefully 10 ml of distilled water, transfer the solution to the 50 ml Nessler tube and add dropwise 10 ml of the sodium hydroxide solution (40→100) under cooling, then dilute to 25 ml with water. Measure the absorbance A obtained from the test solution and A_s obtained from the standard solution at the wave length of 410 mμ against the blank solution procedured in the same way. Concentration of nitrate nitrogen (C ppm) in the test solution was given by the following formula. [numerical formula]

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The present investigation was undertaken to apply a theoretical method to the ventilation of the polluted air in room where carbondioxide in room was not completely diffused. R is defined to be equal to C/C^^-, where C^^- and C are the average carbondioxide concentration in a room and the carbondioxide concentration at a spontaneous place in room, respectively. Assuming that the value of R depends on time and place, the following equation can be obtained. ∂R/∂t=[∂/∂x] [K∂R/∂x] where x is a distance from a source of the evolution of carbondioxide, t is time, and K is a constant (not equal to 0). Implicit difference analogue for the above equation can be obtained as follows, [R (t+Δt)_n-R (t)_n]/Δt=[K/Δx] [{R (t)_n+Δx-R (t)_n}/Δx-{R (t)_n-R (t)_n-Δx}/Δx]=[K/(Δx)²] [R (t)_n+Δx-2R (t)_n+R (t)_n-Δx] where R (t)_n and R (t+Δt)_n are the R values at t and (t+Δt) in a place n, respectively, R (t)_n+Δx and R (t)_n-Δx are the R values at time t in place (n+Δx) and (n-Δx), respectively. A place of the source of crbon dioxide, (n-Δx), n and (n+Δx) are on a straight line in room, n is a center of a diagonal of room and the distance from a source of the carbon dioxide evolution to n is 7.80m, and Δx=5.50m. Assuming that the value of R at n is equal to 1 without regard to tim, or R (0)_n=R (1)_n=………=R (t)_n=R (t+Δt)_n=1 it will be noted that a following equation is obtained, R (t)_n+Δx+R (t)_n-Δx=2R (t)_n=2…………………(1) It was found experimentally that the equation (1) was appropriate from the value of R at place of (n+Δx) and (n-Δx).

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Method for the measurement of cleaning effects of automatic dish-washers has been investigated. The mothod consists of measurement of residual fat and paste. The points of this method were as follows. (1) On the test of residual fat. As quantitative correlation had been ascertained between residual fat and oilred, residual fat was determined by means of the determination of residual oilred on the tablewares. The determination was carried out after mixture of tallow and oilred was painted on the tablewares and washed. (2) On the test of residual paste. For the convenience of determination, CMC was used as paste material and sodium polyacrylate was added to increase the CMC viscosity. This paste was painted on the tablewares and washed. The residual CMC was determined by the reaction with chromotropic acid. The method was applied to the various automatic dish-washers and found to be useful.

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