Water, Carbon Dioxide-Free

P2. 0.025m Phosphate buffer. Dissolve 3.40g of KH2P04 and 3.55 g of Na2HP04 (dried for 2 hours at 110-113 °C) in carbon-dioxide-free water and dilute to 1 kg. The solution is stable when protected from undue exposure to the atmosphere. 

Dissolve 2.5 g in carbon dioxide-free water R, and dilute to 25 mL with the same solvent. The solution is clear, and not more intensely colored than intensity 6 of the range of reference solutions of the most appropriate color. 

Experiments were made in a nitrogen atmosphere using reagent grade chemicals and triply distilled carbon dioxide-free water. Standard solutions of... 

Test for sensitivity A mixture of 0.1 mLof the methyl orange solution and 100 mL of carbon dioxide-free water K is yellow. Not mine than 0.1 mL of 0.1 N hydrochloric acid is required iti change tine Culii tu red. 

Acidity (as acetic acid) Mix 38 mL of sample with an equal volume of carbon dioxide-free water, add 0.1 mL of phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Not more than 0.1 mL is required to produce a pink color. Aldehydes (as formaldehyde) Prepare a Sample Solution by diluting 2.5 mL of sample with 7.5 mL of water. Prepare a Standard Solution containing 40 p,g of formaldehyde in 10 mL of water. Add 0.15 mL of a 5% solution of 5,5-dimethyl-1,3-cyclohexanedione in alcohol to each solution, and evaporate on a steam bath until the Acetone is volatilized. Dilute to 10 mL with water, and cool quickly in an ice bath while stirring vigorously. Any turbidity produced in the Sample Solution does not exceed that produced in the Standard Solution. 

Solubility in Water Mix 38 mL of sample with an equal volume of carbon dioxide-free water. The solution remains clear for at least 30 min. 

Optical (Specific) Rotation Determine as directed under Optical (Specific) Rotation, Appendix IIB, using a solution containing 1 g of sample in 10 mL of carbon dioxide-free water. 

Assay Prepare an acetylating reagent, within one week of use, by mixing 3.4 mL of water and 130 mL of acetic anhydride with 1000 mL of anhydrous pyridine. For the Assay, pipet 20 mL of this reagent into a 250-mL iodine flask, and add about 1 g of sample, accurately weighed. Attach a dry reflux condenser to the flask, and reflux for 1 h. Allow the flask to cool to room temperature, then rinse the condenser with 50 mL of chilled (10°) carbon dioxide-free water, allowing the water to drain into the flask. Stopper the flask, cool to below 20°, add... 

Acidity (as H2SO4) Dilute 9 mL (10 g) of sample in 90 mL of carbon dioxide-free water, add methyl red TS, and titrate with 0.02 N sodium hydroxide. The volume of sodium hydroxide solution should not be more than 3 mL greater than the volume required for a blank test on 90 mL of the water used for dilution. 

Quantitatively transfer the contents of the conical flask into a 500-mL distillation flask fitted with a Kjeldahl trap and a water-cooled condenser, the delivery tube of which extends well beneath the surface of a mixture of 150 mL of carbon dioxide-free water and 20.0 mL of 0.1 A hydrochloric acid in a receiving flask. Add 20 mL of a 1 10 sodium hydroxide solution to the distillation flask, seal the connections, and then begin heating carefully to avoid excessive foaming. Continue heating until 80 to 120 mL of distillate has been collected. Add a few drops of methyl red TS to the receiving flask,... 

Iodate Dissolve 1.1 g of sample in sufficient ammonia- and carbon dioxide-free water to make 10 mL of solution, and transfer to a color-comparison tube. Add 1 mL of starch TS and 0.25 mL of 1 A sulfuric acid, mix, and compare the color with that of a control containing, in each 10 mL, 100 mg of Potassium Iodide, 1 mL of standard iodate solution (prepared by diluting 1 mL of a 1 2500 solution of potassium iodate to 100 mL with water), 1 mL of starch TS, and 0.25 mL of 1 N sulfuric acid. Any color in the sample solution does not exceed that in the control. 

Thiosulfate and Barium Dissolve 500 mg of sample in 10 mL of ammonia- and carbon dioxide-free water, and add 2 drops of diluted sulfuric acid. No turbidity develops within 1 min. 

Loss on Ignition Transfer about 5 g of sample, previously dried at 105° for 2 h and accurately weighed, into a suitable tared crucible, and ignite at 900° to constant weight. pH (20% slurry) Determine as directed under pH Determination, Appendix IIB, using a 1 5 slurry prepared with carbon dioxide-free water. 

Titratable Acidity (as Lactic Acid) Accurately weigh a portion of the finely ground dry sample or liquid equivalent to 10.0 g of total solids based on the value obtained under Loss on Drying (above), and transfer into a 500-mL conical flask. Add 100 mL of carbon dioxide-free water, and stir for 1 min. Allow to stand for 1 h at room temperature. Add 0.5 mL of phenolphthalein TS, and titrate with 0.1 A sodium hydroxide to a pink endpoint that persists for 30 s. Each milliliter of 0.1 A sodium hydroxide is equivalent to 9.008 mg of lactic acid. 

Certain of the following test solutions are intended for use as acid-base indicators in volumetric analyses. Such solutions should be adjusted so that when 0.15 mL of the indicator solution is added to 25 mL of carbon dioxide-free water, 0.25 mL of 0.02 N acid or alkali, respectively, will produce the characteristic color change. 

Sodium Hydroxide, 1N (40.00 g NaOH per 1000 mL) Dissolve about 40 g of sodium hydroxide (NaOH) in about 1000 mL of carbon dioxide-free water. Shake the mixture thoroughly, and allow it to stand overnight in a stoppered bottle. Standardize the clear liquid as follows Transfer about 5 g of primary standard potassium biphthalate [ KHCgH4(COO )2], previously dried at 105° for 2 h and accurately weighed, to a flask, and dissolve it in 75 mL of carbon dioxide-free water. If the potassium biphthalate is in the form of large crystals, cmsh it before drying. To the flask add 2 drops of Phenolphthalein TS, and titrate with the sodium hydroxide solution to a permanent pink color. Calculate the normality. Each 204.2 mg of potassium biphthalate is equivalent to 1 mL of 1 N Sodium Hydroxide. 

Acidity/alkalinity pH 4.3-4.7 (1% w/v solution in carbon dioxide-free water)... 

Bacteriostatic water for injection carbon dioxide-free water ... 

Carbon dioxide-free water Cationic emulsifying wax Ceratonia extract Cetylpyridinium bromide Chlorhexidine acetate Chlorhexidine gluconate Chlorhexidine hydrochloride Chlorodifluoromethane Chlorophenoxyethanol Com syrup solids m-Cresol o-Cresol p-Cresol... 

It is often preferable for physiological purposes to use buffer systems other than the boric acid-borate mixtures. L. Michaelis has found that mixtures of veronal (diethylbarbituric acid) with its sodium salt show a satisfactory buffer action in the neighborhood of pH = 8.0. Pure commercial samples of the sodium salt of veronal are readily available, and may be used frequently without previous recrystallization. Buffer mixtures can be prepared by adding hydrochloric acid to the salt. This compound is water-free, and should suffer no loss in weight when dried at 100°. A 0.1 N solution in water requires exactly an equivalent quantity of 0.1 N hydrochloric acid when neutralized against methyl red. A stock solution should contain 10.30 g. of the sodium salt per 500 c.c. Only carbon dioxide free water should be used. 

L. Michaelis has reported also a combination of veronal and acetate buffers which, due to the addition of an appropriate amount of sodium chloride, have the same ionic strength as a salt solution isotonic with blood. The original solution is 1/7 molar with respect to sodium acetate and the sodium salt of veronal, 500 c.c. of solution (in carbon dioxide-free water) containing 9.714 g.-of sodium acetate (CH3C00Na-3H20) and 14.714 g. of the veronal salt. Five c.c. portions of this solution are treated with 2 c.c. of an 8.5% NaCl solution, with a c.c. 0.1 N HCl, and with (18 — a) c.c. of water. The following table shows how o and pH (hydrogen electrode 25°) are related. 

Measurements of pH in extremely dilute solutions of strong bases are extremely difficult because of the sensitivity of such solutions to carbon dioxide. Obviously one must employ iso-hydric indicator solutions. The author has proceeded in the following manner. To carbon dioxide free water in the cylinder shown in Fig. 22 were added in rapid succession dilute alkali from a micro burette and then the indicator mixture. The pH was calculated from the known hydroxyl ion concentration by... 

Permanent hardness may be determined in the following manner. A quantity of the water measuring 100 ml is boiled gently for 45 minutes, cooled, and made up to its original volume with cold carbon-dioxide-free water. After mixing well, the precipitated temporary hardness is removed by filtration, and the permanent hardness determined in the filtrate by titration with soap solution. The temporary hardness will be the difference between the total and the permanent hardnesses. 

To standardize the pH meter, select two buffer solutions for standardization whose difference in pH does not exceed 4 units, and such that the expected pH of the material under test falls between them. Fill the cell with one of the buffer solutions for standardization at the temperature at which the test material is to be measured. Set the control "temperature" at the temperature of the solution, and adjust the calibration control to make the observed pH value identical with that tabulated. Rinse the electrodes and the cell with several portions of the second buffer solution for standardization, then fill the cell with it, at the same temperature as the material to be measured. The pH of the second buffer solution is within +0.07 pH emit of the tabulated value. If a larger deviation is noted, examine the electrodes and, if they are faulty, replace them. Adjust the "slope" or "temperature" control to make the observed pH value identical with that tabulated. Repeat the standardization tmtil both buffer solutions for standardization give observed pH values within 0.02 pH unit of the tabulated value without further adjustment of the control. When the system functions satisfactorily, rinse the electrodes and cell several times with a few portions of the test material, fill the cell with the test material, and read the pH value. Use carbon dioxide-free water for solution or dilution of test material in pH determinations. In all pH measurements, allow a sufficient time for stabilization. 

Solubility in carbon dioxide-free water. The solubility of calcite in distilled water free of carbon dioxide is 14 mg/1 at 25 °C, rising to 18 mg/1 at 75 °C. That of aragonite increases from 15.3 mg/1 at 25 °C to 19.0 mg/1 at 75 °C [3.1]. However, these values are only of academic interest, as natural water contains dissolved carbon dioxide. 

Apparent pK s were measured by titration of ca. 0.01 M solutions of the hydrochloride salts in 60 40 dimethylformamide—carbon dioxide-free water with 0.1 N NaOH at 25°. A Beckman model G pH meter was used. The listed values are the averages of at least two determinations."... 

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