Studies of the chemical durability of glass by an interferometer method

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The electrode function (pH response) of 8, series of potash-silica (K20-Si02) glasses was determined and a comparison made with the hygroscopicity of the glasses. All the K20-Si02 glasses investigated showed a very high hygroscopicity, with an accompanying sensitive pH response. However, between pH 2 and 4, glasses of 71.8 and 73.6 percent Si02 gave pHresponse values higher than the 59 millivolts per pH predictable from the Nernst equation.Electrodes prepared from all members of the series demonstrated large voltage departures from the straight-line relation with increasing alkalinity of the buffer solutions. For a glass of 75.76 percent Si02 content, the voltage departures were compared with the chemical durability of the glass and also with the sodium-ion concentration, [Na+l, of the BrittonRobinson universal buffer solutions used. The voltage departures correlated with the magnitude of the attack much more convincingly than with the pNa.For several chosen pH values, the voltage departures for the electrodes of these glasses when plotted with reference to their Si02 content gave curves that indicated a sharp change in slope near 74 percent of silica. A corresponding change in slope was also shown by the hy groscopicity-percentage-silica curve.

Section: Methodsmentioning

confidence: 95%

Electrode function (pH response) of potash-silica glasses

Hubbard¹

1946

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“…The ch emical durability (reported as attack:) of t he glass was determined by th e interferom eter method [4,13]. This procedm e offered a rapid means of determining th e amoun t of solution or swelling of th e glass over a wide range of conditions under circum stances in which th e conventional analytical methods would be time-consuming, unreliable, or even impossible.…”

Section: Methodsmentioning

confidence: 99%

Voltage anomalies of the glass electrode and the chemical durability of the glass

Hubbard¹,

Rynders²

1947

Additional ,,·o rk ha been done on the correspondence between voltage departures (errors) of elecl rodes p repared fr om Com ing 01 5 g lass and t he change in t he chemical durabili ty of the g lass . The results con firm and extend t he earli er findin gs that voltage depart ures of the elcetrod e arc accompanied by durabili ty chan ges of t he glass. Th e pronoullced voltage departures in the a lkaline region an d in h ydrofluoric acid solution s are accompanied by conspie uou attack of the glass. Dilu te solu t ions of acids that do not form so luble compounds of s ilica cause swell ing of the glass. Th is s,,·el li ng is repressed as the concent ralion of lhe solution s is in creased . As i to be expected from the di stribution Jaw and Donnan membran e conside rations, th is repression of swellin g was also br ought aQout by high CQJ1cent rations of orga ni c acids and salts as well as b y the so-called "stro ng" a ids.The attac k of Corning 01 5 glass by alkaline solutions of different ion s was found to be in the orde r, Na+> Li+> K +> Ba++> NH.+, ,,"hich is the same order dicta ted for these ions by the voltage depar t ure data.

“…in table 2 and. figure 1 when compared with results published years earlier [4] show the need. for improvement in the chemical durability of these glasses; their poor durabilities have been contributory to the excessive deterioration of optical instruments and spectacle lenses under condition.s of high atmospheric temperature and relative humidity [23].…”

mentioning

confidence: 71%

“…The ligh t source used as a standard of length was the 5876 A line of th e h elium spectrum. For th e range pH 1.8 to 11.8 the BrittonRobinson universal buffers were used [10, table 57c] ; for th e more acid exposures aqueous solutions of H 2S0 4 were employed. All exposures were made at 80° C and a durability comparison was m ade on a 6 hI' basis, al though some of the exposures were limited to shorter periods.…”

Section: Methodsmentioning

confidence: 99%

Some properties of a glass used in paper manufacture

O'Leary¹,

Hubbard²

1955

The chemi cal durability, heterogeneou s equilibria, h ygroscopicity, pH response, disper·sal, and t hermal ex pa nsion characteristics of a fib er glass used in paper manufacture were inves tiga ted . The chemi cal durabili ty of t his gl as~, was found to be ver y poor between pH 2 and pH -2, apparently du e to the high alumina"and low silica composition. Above and below t his range t he chemical durability greatly improved , showing with t he interferom eter no detectable attack for expos ures of 6 hours at 80° C either in high concentrations of H 2 S04, or between pH 4 and pH 8. At a lkalinities above pH 8 t h e durabili ty again decreased as is characteristic of man y silica te gla sses. In a ddi tion, t he h eterogeneous equilibria at the solu Lion-glass interface, using Ag (NH 3lz+ ions as indi cator , showed t he fib er glass when leached at pH 4.1. to have an un even distribution of migratable ions between t h e negatively charged glass surface and ambient aqueoll s sol utions, to a greater extent t han m ost commercial gl a~se~. In acco rd wi th the very low h ygroscopici ty and poor chemical durabi lity, clcctrodes prcpa rcd fro m Lhis glass gave no defini te r esponse Lo h ydrogen ion activi Ly of the ambient solli tions. Thc di spersal ch aracteri stics of t he fib ers in aqueo us solu tions foll ow t he "cri t ical" poin ts indicated l ,by t h e chemi cal du rabili ty CllI'VC co vering t he range fr o m pH -8.1 to pH 11 .8. Th c a nnealing and softelling temperatures a s obtained from Lhe r es pective expansion cur ves \I'ere found to be higher fo r t he fi ber glass than for either P y rex 7740 or Kimble N 51-A.Th c chemi cal durabili ty data, t he acid t itrat ion of sodium Silicate, and t he di s persal-pH series a re consistent wi th t he fi ndin gs of O'Leary et al. in emphasizing p H 2.9 as a cri t ical co nditi on for Lhc m ost slI cccss ful produ ction of paper from fib ers o f t his glass.