Journal of Agricultural Research . ons from this, for the solution used in the spectrophotometermust contain not more than 4 milligrams of carotin per liter, becausegreater concentrations will give a transmittancy which can not be usedin obtaining data from the graphs in Figure 3. The method will be described in a later paper. 394 Journal of Agricultural Research voi. xxvi,no. 9. For the experiments in this paper each cell had an inside measurementof 2 cm. The 2 cm. refers to the thickness of the solution through whichthe light passes and not to the diameter of the cell. One cell is filled wit
Journal of Agricultural Research . ons from this, for the solution used in the spectrophotometermust contain not more than 4 milligrams of carotin per liter, becausegreater concentrations will give a transmittancy which can not be usedin obtaining data from the graphs in Figure 3. The method will be described in a later paper. 394 Journal of Agricultural Research voi. xxvi,no. 9. For the experiments in this paper each cell had an inside measurementof 2 cm. The 2 cm. refers to the thickness of the solution through whichthe light passes and not to the diameter of the cell. One cell is filled withthe carotin solution and the other with the solvent. The cells are thenplaced in the holder on the instrument. In measuring transmittancies,as in this investigation, the cell containing the carotin solution is placedin one beam of light, and a similar cell, containing the solvent, is placedin the other beam. These cells are interchanged and the nicol is rotatedin each case until an intensity match is obtained.^^ The transmittancy. 50 Fig. VC 30 20 A-f/LL-S/iAAfJ :y- CA^077M F^/? UTS/i C. -Lovibond slide readings plotted to show the results of carotin in ether. /O O obtained from different concentrations is then obtained as the product of the cotangent of the angle in one case-by the tangent of the angle in the other. With an ethereal solution of carotin, using the line ,angles were read as follows; Oj, ; Gj, The cotangent of 61times the tangent of G, gives the value for the transmittancy of thesolution. At the left-hand side of Figure 3, the value for the trans-mittancy is found. This point on the graph represents mgm. of caro-tin per liter. The transmittancy, and consequently the concentration, ofany solution of carotin of unknown concentration may be obtained inthis way. 1* For each position of the cells there are four settings of the nicol for which an intensity match can beobtained; that is, one in each quadrant of the circle. The
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