23│ 8.68│ 8.27│ 7.85│ 7.43│ 7.00│ .0083 24│ 8.53│ 8.12│ 7.71│ 7.30│ 6.87│ .0083 25│ 8.38│ 7.96│ 7.56│ 7.15│ 6.74│ .0082 │ │ │ │ │ │ 26│ 8.22│ 7.81│ 7.42│ 7.02│ 6.61│ .0080 27│ 8.07│ 7.67│ 7.28│ 6.88│ 6.49│ .0079 28│ 7.92│ 7.53│ 7.14│ 6.75│ 6.37│ .0078 29│ 7.77│ 7.39│ 7.00│ 6.62│ 6.25│ .0076 30│ 7.63│ 7.25│ 6.86│ 6.49│ 6.13│ .0075 ─────────────┴────────┴────────┴────────┴────────┴────────┴─────────── Footnote F: Under any other barometric pressure, B, the solubility can be obtained from the corresponding value in the table by the formula: S´ = S(B/760) = S(B´/29.92) in which S´ = Solubility at B or B´, S = Solubility at 760 mm. or 29.92 inches, B = Barometric pressure in mm., and B´ = Barometric pressure in inches. ETHER-SOLUBLE MATTER.[44] Evaporate 500 cc. of the sample in a porcelain evaporating dish to a volume of about 50 cc. By means of a rubber-tipped glass rod remove to the bottom of the dish the solid matter attached to the sides, and add normal sulfuric acid to neutralize the alkalinity. Do not use an excess of acid. Then evaporate the contents of the dish to dryness. Treat the dry residue with boiling ether, rubbing the bottom and sides of the dish to insure complete solution of fat. Three extractions with ether are required. Filter the ether solution through a 5 cm. filter into a weighed flask having a wide mouth. Evaporate the ether slowly, and dry the flask at 100° C. for 30 minutes. The increase in weight of the flask gives the amount of fats, or, in more precise language, the ether-soluble matter. An excess of acid gives too high results because of the formation of fatty-acid residues. RELATIVE STABILITY OF EFFLUENTS.[78] _Reagent._—Methylene blue solution. A 0.05 per cent aqueous solution of methylene blue, preferably the double zinc salt or commercial variety.[60b] _Collection of sample._—Collect the sample in a glass-stoppered bottle holding approximately 150 cc. If the dissolved oxygen is low observe precautions similar to those used in collecting samples for dissolved oxygen (p. 66).