Gravimetric determination after distillation

On sampling, free dissolved carbon dioxide and its compounds are fixed as carbonate by filling the water samples into flasks which are charged with sodium hydroxide solution or calcium oxide. In closed apparatus in the laboratory, add acid to the weakly alkaline sample, liberating carbon dioxide, bind the carbon dioxide on soda-asbestos and weigh. 

The method is particularly suited to the determination of CO2 in waters rich in carbon dioxide whose CO2 content (total carbon dioxide) is 1000 mg/1 or higher. 

Flat-bottomed flasks with ground joint, ground glass stopper and safety groove in the stopper to secure for transport, volume 250 ml and 500 ml. 

A Wash bottle containing sulphuric acid (1.84 g/ml) it serves as a bubble 

B Absorption tower containing soda lime and with a cotton-wool plug at the 

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In addition both the free and bound carbon dioxide are fixed with CaO or NaOH and the total carbonic acid level is determined in the laboratory by means of "gravimetric measurement after distillation" (as described in Section 3.2. "Total Carbon Dioxide") (c). 

Gravimetric determination as barium sulphate after distillation General... 

B) Qualitative Determination. Exactly 25 c.c. of the distilled spirit are boiled with about 30 c.c. of water, 0 5 c.c. of syrupy phosphoric acid and 0-5 c.c. of aniline under a reflux condenser for half an hour. After cooling,the bulk of the liquid is distilled and the distillate collected in a 50 c.c. measuring flask and made up to volume with water. The ketones are then determined (see section 2), 20 c.c. or 4 c.c. being used according as the gravimetric or volumetric method is employed. 

To prepare the solution we used zirconium nitrate containing 1.5 to 2.1% of hafnium in a ratio to the sum of zirconium and hafnium oxides (2 Zr(Hf)02). Initial solutions of zirconium nitrate with different concentrations of salts and nitric acid have been prepared by dissolving a concentrated water solution of zirconium nitrate salts. TBF, dissolved by o-xylol has been used as extraction media. Trials have been done in batches. The extraction media, previously saturated by nitric acid, is mixed with water solution (20 ml at a time) for 15 minutes on a vibration apparatus. Re-extraction has been done by two-step vibration of the organic phase with equal volumes of distilled water. The water phase was, after extraction and reextraction, analyzed gravimetrically to find out the contents of the sum of zirconium and hafnium oxides. Hafnium contents were determined by spectral analysis. Nitric acid concentration has been determined by titration. 

To determine cell mass, the hairy roots were harvested, rinsed with distilled water, and the extra water was eliminated. Treated hairy roots were measured as fresh weight and dry weight. The dry weight was measured gravimetrically after drying the roots at 60°C for 24 h. 

To promote good lipid accumulation in the cells, the culture was transferred to a nitrogen-absent medium. The rate of depletion of soluble potassium nitrate in culture medium was determined with Hitachi HPLC L6000. And the fluorescent intensity of the Nile Red-dyed microalgal cells was measured by Hitachi fluorescent spectrophotometer UV-2000. Stainability with Nile Red was determined as fluorescent intensity at 575 nm per cell density. After the cultivation, cells were harvested by centrifugation, washed twice with distilled water and lyophilized. Cellular lipid was extracted by the method of Bligh and Dyer [5] and determined gravimetrically. 

For the analysis of molybdenum, the sample is decomposed by fuming with a few drops of nitric acid and sulfuric acid in a platinum crucible and the molybdenum is determined gravimetrically7 as the 8-quinolinol complex. From the filtrate, potassium is determined gravimetrically as K2S04. Fluoride is determined by titration with a standard solution of thorium nitrate using sodium alizarinsulfonate as indicator, after steam distillation of fluorosilicic acid.8 The determination of the oxidation state of molybdenum is carried out by oxidizing a known amount of the compound with a known amount of potassium dichromate in hot 2 N sulfuric acid and titrating the excess dichromate with standard Fe2+ solution. 

Identified by Heins et al. (1966) in the headspace over coffee beans by one of the first capillary-GC/MS coupling. The ion M + 1 (mjz = 117) was one of the ions used by Dyszel (1985) when using thermo-gravimetric analysis/atmospheric pressure chemical ionization mass spectrometry (TGA/APCIMS) for determining the origin of green coffee. It was found after simultaneous distillation-extraction and analysis by GC/MS by Spadone et ai (1990) in a Puerto Rico Rio coffee, but not in a healthy variety. It was one of the compounds emitted by fresh red coffee berries in two robusta varieties (Mathieu et al., 1996), and was found to decrease if the berries were left on the plant after the red stage (Mathieu et al., 1998). 

Pentose sugars and pentosans may be quantitatively estimated by conversion into furfural by distillation with hydrochloric acid. The amount of furfural is determined gravimetrically after precipitation with phloroglu-cinol, barbituric acid, or thiobarbituric acid, or volumetrically by titration with bromine or phenylhydrazine. Approximately theoretical yields of furfural are obtained if the furfural is removed rapidly from the reaction mixture by steam distillation ... 

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