Volatile acid solution preparation

Preparation of Volatile Acids Solutions in Various Media. Samples of 150 g 90/10 oil/water blend containing 500 ppm concentrations of acetic, propionic, butyric, valeric, and caproic acids were micro-waved 0, 1, 2, and 3 minutes in a 600 Watt G.E. Microwave Oven. Temperatures were recorded and a duplicate sample was heated to the same temperatures in a conventional oven. Samples were heated in open containers to permit the loss of acids during heating. 

Laboratory-scale preparations of ammonia and volatile acid solutions intended for use in trace metal analysis have been successfully performed by isothermal distillation, usually at room temperamres. In this technique, two beakers, one containing the chemical being purified and the other holding pure water, are placed together in a sealed closed container for a few days. The volatile component becomes uniformly shared between the contents of the two vessels and nonvolatile impurities remain in the original beaker. 

Qua.driva.Ient, Zirconium tetrafluoride is prepared by fluorination of zirconium metal, but this is hampered by the low volatility of the tetrafluoride which coats the surface of the metal. An effective method is the halogen exchange between flowing hydrogen fluoride gas and zirconium tetrachloride at 300°C. Large volumes are produced by the addition of concentrated hydrofluoric acid to a concentrated nitric acid solution of zirconium zirconium tetrafluoride monohydrate [14956-11-3] precipitates (69). The recovered crystals ate dried and treated with hydrogen fluoride gas at 450°C in a fluid-bed reactor. The thermal dissociation of fluorozirconates also yields zirconium tetrafluoride. 

Isopiestic or isothermal distillation. This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of the material to be purified, in a desiccator. The desiccator is sealed and left to stand at room temperature for several days. The volatile components distribute themselves between the two beakers whereas the non-volatile contaminants remain in the original beaker. This technique has afforded metal-free pure solutions of ammonia, hydrochloric acid and hydrogen fluoride. 

A filtered solution, prepared by heating mercuric oxide with a slight excess of perchloric acid, after standing for several months precipitated a little unidentified white solid. This (but not the supernatant liquid) was very shock sensitive, and detonated as it was being rinsed out with water. (Traces of a volatile amine may have been absorbed into the acid liquor to give an amminemercury perchlorate, expected to be explosive). 

This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace... 

This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of... 

A hydrobromic acid solution is prepared in a 5-I. round-bottom flask by the reduction of 1000 g. of bromine in the presence of 1100 g. of cracked ice. Experimental details have been given under (A) Hydrobromic Acid. A mixture of 2075 g. of aqueous (48 per cent) hydrobromic acid and 600 g. of concentrated sulfuric add may be used in place of the above reduction mixture. After the addition of 500 g. of ordinary 92 per cent ethyl alcohol, the flask is attached to a long condenser set ready for distillation and 1000 g. of concentrated sulfuric acid are slowly added through a separatory funnel. Because of the volatility of ethyl bromide, the mixture is not heated under reflux, but is subjected instead to slow distillation. The end of the condenser is provided with an adapter tube, and the distillate Is collected in a flask containing ice water. The crude... 

Chemically pure vanadium pentoxide is alternatively prepared by precipitating insoluble mercurous vanadate, HgV03, from a neutral solution of a vanadate, and distilling off the mercury, or by ignition of vanadium salts of volatile acids, for example, vanadium oxytrichloride, VOCl3. The oxide also results from the oxidation of any of the lower oxides, or by the electrolysis of a solution of sodium vanadate or copper vanadate, using a divided cell the last method yields a product of 98 per cent, purity.2... 

To prepare mobile phases, clean HPLC-grade solvent must be used along with clean solvent bottles. Since most of the organic solvents are volatile, they should be well sealed in solvent bottles after preparation. Acetic acid is subject to evaporation, causing the pH of the aqueous acetic acid solution to shift. Freshly prepared acetic acid in water is recommended for each set of analyses. The calculated pH of 1% acetic acid in water is -2.7 however, it is suggested to check the pH of the acid solution each time it is prepared to assure its pH is >2. 

Pipet a 10-mL sample into a 100-mL cassia flask fitted with a stopper, and add 50 mL of a freshly prepared 30 in 100 solution of sodium sulfite. Add 2 drops of phenolphthalein TS, and neutralize with 50% (by volume) acetic acid solution. Heat the mixture in a boiling water bath, and shake the flask repeatedly, neutralizing the mixture from time to time by the addition of a few drops of the 50% acetic acid solution, stoppering the flask to prevent loss of volatile material. After no coloration appears upon the addition of a few more drops of phenolphthalein TS and heating for 15 min, cool to room temperature. When the liquids have separated completely, add sufficient sodium sulfite solution to raise the lower level of the oily layer within the graduated portion of the neck of the flask. Calculate the percentage, by volume, of the aldehyde or ketone by the equation... 

This is one of the earliest methods of microsphere manufacture. The polymer and drug must be soluble in an organic solvent, frequently methylene chloride. The solution containing the polymer and the drug may be dispersed in an aqueous phase to form droplets. Continuous mixing and elevated temperatures may be employed to evaporate the more volatile organic solvent and leave the solid polymer-drug particles suspended in an aqueous medium. The particles are finally filtered from the suspension. Fig. 3 shows polylactic acid particles prepared in this manner. ... 

The freeze-drying method is one of solvent volatilization, but it differs from the common solvent evaporation techniques in that the solvent is sublimed from the solid state. A solution, prepared by means of soluble salts or by dissolving metals in acid, is frozen and the solid solvent, usually water in the form of ice, is sublimed away giving the dried salts. The process gives high surface area powders of excellent chemical homogeneity. 

Small quantities of the hydrogen halides (their solutions are called hydrohalic acids) and other volatile acids are usually prepared by adding concentrated nonvolatile acids to the appropriate salts. (Sulfuric and phosphoric acids are classified as nonvolatile acids because they have much higher boiling points than other common acids.) The reactions of concentrated sulfuric acid with solid sodium fluoride and sodium chloride produce gaseous hydrogen fluoride and hydrogen chloride, respectively. 

A volatile acid such as nitric acid, HNO3, can be prepared by adding concentrated H2SO4 to a salt of the acid, (a) Write the chemical equation for the reaction of H2SO4 with sodium nitrate (called Chile saltpeter), (b) A dilute aqueous solution of H2SO4 cannot be used. Why ... 

Esterification of acids [1, 192, at end]. In the routine preparation of methyl esters for characterization by gas chromatography by ether extraction and treatment with diazomethane, the extraction step is troublesome in the case of water-soluble acids (e.g., diacids, hydroxy acids). A simple expedient is as follows 143 Assuming that the fatty acid solution is alkaline and free of neutral materials, acidify to pH 3-4 with hydrochloric acid (excess would be converted into methyl chloride), cool (to prevent loss of diazomethane by volatilization), and cautiously (bubbling) add an ethereal solution of diazomethane. 

Typical Aqueous Solution Preparation (70% non-volatile in 2-Bu-toxyethanol). A cold cut was made of 105 grams of the epoxy ester and 45 grams of 2-butoxyethanol. To this solution were added 8.41 grams triemylamine, 100% neutralization based on the pretitrated acidity. Wa-... 

---