•The secret to cool bodies and glazes is a lot of testing.
•The secret to know what to test is material and chemistry knowledge.
•The secret to learning from testing is documentation.
•The place to test, do the chemistry and document is an account at https://insight-live.com
•The place to get the knowledge is https://digitalfire.com
Rubidium and Cesium Toxicology
Atomic weight: Rb 85.468, Cs 132.905
Rubidium and Cesium are monovalent alkaline metals among those which present the highest number of protons and atomic weight. Their activity increases with the increase in the atomic number, resulting in extending the range of
vitrification in particular in the ternary glasses of the M2O-CaO-SiO2 type comparatively to other alkaline metals which have a smaller atomic weight. Contrary to other alkaline metals, they do not present phase separations by non-miscibility in binary
glasses of the Rb2O-SiO2 and Cs2O-SiO2 types . The phase separation occurs in the borate binary systems Rb2O-B2O3 and Cs2O-B2O3.
The ionic radius of alkaline metals increases with the increase in the atomic number, thus the ion Cesium is the largest among those monovalent metals. This characteristic relates to the immobility of its ions in an electric
field and its extremely positive effects on the insulating properties of glasses. On another side, Cesium shows the lowest bonding strength, as indicated by the thermal expansion of Cesium glasses, which is the highest among that of glasses containing
Experimental fusions of silica-lime glasses with equivalent molar contents of Rb2O or Cs2O showed that these glasses melt and solidify at temperatures similar to those corresponding respectively to potassium and sodium glasses.
Binary glasses with Cesium melt at 800-1000°C and crystallize with difficulty. They do not attack excessively refractory structures and they are not difficult to refine. Their viscosity increases with the atomic number of the alkaline metal used.
These two elements improve considerably the fusibility of the binary glasses R2O-SiO2, and glasses with multiple components.
Cesium volitilizes easily during fusion,
in particular if it is introduced in the CsNO3 form. The resulting
losses during heating depend on the rate of the reactivity between
CsNO3 and the other components of the composition. The optimal temperature of softening is 700°C, when CsNO3 reacts quickly with SiO2. Great losses by volatilization take place when the temperature of reaction is maintained too high or too.
The reaction of CsNO3 with B2O3 starts at approximately 350°C, where the losses by volatilization of borate glasses are also the lowest. The losses by volatilization of Cesium glasses can be decreased by using finely ground
Effects of Rubidium and Cesium on the properties of glass :
Density and refraction index :
they are increased considerably by Rb and Cs comparatively to other alkaline metals. The density of Silica-Lime-Rubidium glasses varies between 2.6 and 3.0 g/cm³, thus reaching the values characteristic of leaded crystal
Thermal expansion :
it is increased by these two elements,
more than by Na or K, in such a way that for a Cs2O-CaO-SiO2
glass, containing 30% molar of Cs2O, the dilation coefficient
reaches a value that may go to 195 X 10-7 °K-1 (between 20
It increases with the increase in the atomic number of the alkaline metal used.
Electric properties :
they are influenced by Rb and Cs on an extreme level. With silico-calcic-alkaline glasses, the substitution of Cs2O by Na2O increases the electrical resistance in a range of values which exceeds by far that of the effects
obtained with lead and barium. In this way, the effects of Rubidium are similar to those of lead and thallium. Since the permittivity of silica-lime-alkaline glasses increases from lithium towards potassium, the three elements potassium, rubidium and
cesium present an identical influence. The permittivity of acid borosilicate glasses decreases towards cesium.
Together rubidium and cesium maintain the perfect miscibility which they have with binary glasses even in the case of glasses with multiple components, where they act against the coming of the separation of phases and
devitrification. Glasses containing Rb and Cs are slightly hygroscopic.
Reference : Chemical Approach to Glass, by Milos .B Volf, Elsevier 1984.
Smart.Conseil © July 2004-07-14
Translated by Edouard Bastarache
Out Bound Links
Edouard Bastarache M.D.
Occupational & Environmental Medicine
Author of "Substitutions for Raw Ceramic Materials"
Tracy, QuÃ©bec, CANADA