Volumetric determination following distillation

3 Volumetric determination following distillation General remarks 

With methanol, boric acid forms the readily volatile boric acid methyl ester (6(00113)3), boiling point 68.7 C. This may be volatilized quantitatively from the acid solution in a methanol vapour flow. The ester which 

After boiling away the methanol, CO2 is expelled from the acidified solution. It is neutralized, and treated with mannitol, which - as do other 

The didiol complex reacts or dissociates in aqueous solutions as a complex acid of the strength of acetic acid and can be titrated as such with sodium hydroxide solution. 

This method is particularly suitable for waters with boron contents higher than 0.2 mg/1 and those which are coloured or contain non-filterable turbidities. 

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If the water is coloured or turbid and does not become clear after filtration, the boron may be separated off as boric acid methyl ester (see "Volumetric determination following distillation. Section 3.5.1.3). 

The distillation method [13-15] is based on the separation of ammonia from the sample by distillation from an alkaline medium, followed by volumetric or photometric determination of ammonia in the distillate. In the case of volumetric determination the separated ammonia trapped in a receiver with boric acid in the form of NH4H2BO3 is titrated against standard H2SO4 using a mixed indicator (Methyl Red and Methylene Blue)... 

Determine the parts per million of F in the tap water, (b) For the analysis of toothpaste a 0.3619-g sample was transferred to a 100-mL volumetric flask along with 50.0 mL of TISAB and diluted to volume with distilled water. Three 20.0-mL aliquots were removed, and the potential was measured with an L ion-selective electrode using a saturated calomel electrode as a reference. Live separate 1.00-mL additions of a 100.0-ppm solution of L were added to each, measuring the potential following each addition. 

Fig. 9.10. Apparatus for the determination of molecular weights of air-sensitive compounds by the isothermal distillation technique. Temperature fluctuations of the two solvents are minimized in this illustration by a Dewar filled with water. This apparatus is used in the following manner. In a dry box the sample is placed in a tared tube through sidearm A, the sidearm is then sealed off, the tube and remnant of the sidearm are weighed, and the tube is attached to the apparatus by glassblowing at B. A weighed portion of a standard is introduced into the other bulb, and the filling tube is sealed off. After evacuation, opening of the break-seal, and reevacuation, a measured portion of solvent is distilled into both arms of the apparatus. The process of equilibration is followed by periodic removal and measurement of the solvent from one arm. The solvent may be measured volumetricly in the liquid or gas stales, or by weight.

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