Search results for "Acid concentration"
showing 7 items of 7 documents
Synthesis of single crystalline sub-micron rutile TiO2 rods using hydrothermal treatment in acidic media
2014
Size engineered rutile sub-micron rods were obtained from nanostructured titania under acidic conditions. The synthesis was performed by hydrothermal treatment starting from TiO2-P25 and HCl. The synthesis proceeds in less than two hours and can be up-scaled to several grams in a one-pot reaction by increasing the reaction time. The product is single-phase, and the particles are single crystalline as confirmed by electron diffraction and powder X-ray diffraction analysis. The length of the particles can be varied over a wide range from 100 nm to 1.3 μm by changing the acid concentration. Particle growth is proposed to proceed by a dissolution-recrystallization process via soluble [TiCl6]2− …
Determination of fluoride in rocks, soils, and fluoride-bearing minerals by separation using direct distillation in sulfuric acid medium and spectrop…
1989
Abstract An analytical method for fluoride determination in geological samples is proposed. It is based on a previous fluoride separation by distillation with a Teflon reactor. The variables that influence distillation quantitation (temperature, time, and acid concentration) are optimized. The influence of some species on fluoride recovery during distillation are studied, and conditions to avoid this influence are suggested. Fluoride determination is carried out by means of a spectrophotometric method [La(III)-F−-Alizarin complexone system] (N. T. Crosby, A. L. Dennis, and J. G. Stevens, Analyst (London), 1968, 93, 643–652). The method is applied to the analysis of soils, rocks, and fluorid…
Observations on the use of a sulfuric acid medium for As(V) to As(III) reduction in lodimetric titrations: Application to the determination of total …
1991
Abstract The use of a sulfuric rather than a hydrochloric acid medium for the reduction of As(V) to As(III) by iodide is proposed. Optimum conditions of acid concentration, amount of sodium hydroxide, and time and temperature are established to achieve quantitative reduction. The optimized reduction procedure was applied to the iodimetric determination of total arsenic and compared to a procedure that employs a hydrochloric acid medium. A systematic error of 0.04% was found for the method with a sulfuric acid medium opposed to 0.05% for the method with a hydrochloric acid medium in the reduction step. The proposed modified iodimetric method has been successfully used with some organic sampl…
Der acidolytische abbau von polyoxymethylenen. 18. Mitt. über polyoxymethylene
1962
Beim acidolytischen Abbau von Polyoxymethylendihydraten wurden gaschromatographisch folgende Substanzen identifiziert: Formaldehyd, Wasser, Methanol, Ameisensauremethylester sowie Tri- und Tetraoxymethylen. Die Ausbeute an cyclischen Oligomeren und das Verhaltnis Trioxan/Tetraoxymethylen hangen von der Saure, der Saurekonzentration und der Reaktionszeit ab. Es wird ein Abbaumechanismus vorgeschlagen und diskutiert. In the acidic degradation of polyoxymethylenes the following substances are obtained and identified by gas chromatography: formaldehyde, water, methanol, methyl formate, and also tri- and tetraoxymethylene. The yields of the cyclic oligomers and the ratio trioxane/tetraoxymethyle…
Design of a novel membrane-integrated waste acid recovery process from pickling solution
2019
Abstract Hydrochloric acid pickling is a common practice in steel manufacturing industry. During the process, acid is consumed to dissolve surface oxides and metals ions are accumulated in the solution, which becomes less effective with time. In addition, the costly and risky waste acid disposal is another issue affecting the hot-dip galvanizing industry. In this work, a novel sustainable waste acid recovery process from pickling solutions based on circular approach is proposed to tackle these issues. The innovative system allows (i) the continuous regeneration of pickling solutions to enhance process rate and performance and (ii) minimise the highly expensive and environmentally risky wast…
Studien zum Vorgang der Wasserstoffübertragung, 47.Elektroreduktion von 1,4-Benzoldicarbonitril, 1,4-Diacetylbenzol und Terephthalaldehyd
1978
Die Elektroreduktion von 1,4-Benzoldicarbonitril in Gegenwart von Essigsaure fuhrt bei einem Stromdurchgang von 4.5 Faraday-aquivalenten/mol in 80proz. Ausbeute zu 4-Amino-methylbenzonitril (1). Bei Anwendung von 6 Faraday-aquivalenten/mol konnen geringe Mengen an 4-Methylbenzonitril (2) nachgewiesen werden. Bei der praparativen Elektroreduktion von 1,4-Diacetylbenzol in Gegenwart unterschiedlicher Mengen an Essigsaure entstehen 4-(1-Hydroxyethyl)acetophenon (3), 1,1′-(1,4-Phenylen)diethanol (4) sowie polymere Pinakole 5 in den in Tabelle 1 angegebenen Mengen. Terephthalaldehyd wird in Gegenwart von Essigsaure zu 4-Hydroxymethylbenzaldehyd (6), Terephthalalkohol (7) und einem polymeren Pina…
Determination of fluoride after direct separation from acid medium by collection of its volatile compounds
1989
A method is proposed for determination of fluoride by separation in acid medium followed by ion-selective electrode measurement. The separation is done at temperatures up to 200 °C, without any previous treatment of the sample, in a PTFE reactor designed to ensure the complete absorption of volatile fluoride compounds. The distillation variables (temperature, time and acid concentration) have been optimized and the interference of other various species in the separation step has been studied. The method has been applied to geological samples. The results obtained are statistically satisfactory.