Recherches sur l'obtention, la séparation et la purification du tantale et du niobium, notamment par voie électrolytique. II. Etude d'une méthode de détermination des tensions effectives d'électrolyse et des tensions pratiques de décomposition; application de cette méthode à des solutions cryolithiques d'oxydes

Abstract

Volumen XLIII, Fasciculus VII (1960) -No. 266-267 VII. Ausfarbungen Mit Helianthin. Farbebad: 200 ml Wasser, 0,05 ml Eisessig, 0,5 g GLAUBER-SdZ, 0,1 g Helianthin. 0,50 g Peptidkondensat werden in 20 ml Farbebad von 50" eingetragen; anschliessend wird innert 30 Min. von 50" auf 98" aufgeheizt und 30 Min. auf dieser Temp. gehalten. Man saugt ab und wascht mit Wasser nach, bis das Filtrat farblos ablauft.Mit Malachitgriin. Farbebad: 200 ml Wasser, 0,05 ml Eisessig, 0 , l g Malachitgrun. Farbeprozess gleich wie bei Helianthin. 2163 ZTJSAMMENFASSUNG L-Leucin-methylester wird mit pulverisiertem Natrium zu einem Produkt kondensiert, dessen wasserunloslicher Anteil (60-70% d. Th.) zu 3/5 aus racemischen Leucinpeptiden und zu z/5 aus Di-isobutyl-dioxopiperazin besteht. Nach Abtrennung des Leucin-dioxopiperazins durch Vakuumsublimation oder durch Herauswaschen mit starken Mineralsauren wird ein gereinigtes Polyleucin vom mittleren Kondensationsgrad 10 erhalten.Bei entsprechenden Kondensationen von DL-Asparaginsaure-dimethylester, von DL-Lysin-methylester und von Gemischen dieser Ester werden in Wasser schwerlosliche Kondensate erhalten, die saure undloder basische Seitenketten enthalten.Der wahrscheinliche Reaktionsmechanismus der Natrium-induzierten linearen Kondensation der a-Aminosaureester wird diskutiert.Organisch-chemische Anstal t der Universitat Basel

Electrochemical Production of Al-Si Alloys in Cryolitic Melts in a Laboratory Cell

“…6 In cryolitic melts of 5 wt.% SiO 2 or 5 wt.% SiO 2 and 10% Al 2 O 3 the decomposition voltage of silica was found to be in the range of 1.00-1.25 V in the temperature range of 1000 °C-1030 °C and according to the experimental conditions mentioned in 6,7 where the cathode was either the bottom of a graphite crucible, aluminium, or copper. The observed decomposition voltage of alumina was 1.25-1.45 V, which was in agreement with the values reported in, 8 when cryolitic melts saturated with alumina at 1000 °C were tested using either aluminium or aluminium-silicon alloy(12.5 wt.% Si) as a cathode. 6 When copper was used as a cathode, the decomposition voltage of alumina was 1.50 V at 1030 °C.…”

Electrochemical Behavior of Silicon Species in Cryolite Melt

“…this decreases the decomposition potential to −0.73 V and −0.57 V for CO2 and CO release, respectively. 7 The experimentally measured deposition potentials [8][9][10][11][12][13][14][15][16] are considerably different from these calculated values. For example, the decomposition potential on graphite cathode has been reported as −0.95 ± 0.05 V by several authors, [8][9][10][11][12][13][14][15][16] which is approximately 0.25 V larger than the predicted potential.…”

“…7 The experimentally measured deposition potentials [8][9][10][11][12][13][14][15][16] are considerably different from these calculated values. For example, the decomposition potential on graphite cathode has been reported as −0.95 ± 0.05 V by several authors, [8][9][10][11][12][13][14][15][16] which is approximately 0.25 V larger than the predicted potential. According to Boe et al, 9 this difference is mainly due to the polarization and concentration overpotential, i.e.…”

“…Both graphs display a linear relationship indicating that the silicon deposition is diffusion controlled. The two lines can be expressed as: i p = 1.06 ν 1/2 + 0.49 for raw data and i p = 0.95 ν 1/2 + 0.39 for corrected i p Knowing the slope of the line, it is possible to calculate the diffusion coefficient of the species in an irreversible reaction using Equation 12: 30 i p = 0.496 √ αnFAC * nFDν RT [12] where A is the surface area of the electrode, C * is the bulk concentration of the diffusing species and D is the diffusion coefficient. The exposed surface area of the electrode is 0.51 cm 2 (considering 1 mm as the immersion depth of the electrode).…”

Determination of Cell Potential for Silicon Electrodeposition

“…The reactions decrease the theoretical decomposition potential to À0.73 and À0.57 V for CO 2 and CO release, respectively. [11] The experimentally measured deposition potentials [12][13][14][15][16][17][18][19][20] are considerably different from these calculated values. For example, the decomposition potential on graphite cathode has been reported between À0.80 and À1 V, [12][13][14][15][16][17][18][19][20] which is approximately 0.25 V larger than the predicted potential.…”