Electrode function (pH response) of potash-silica glasses

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.

Section: Sodium Hyd Roxide Solutionssupporting

confidence: 86%

Section: Sodium Hyd Roxide Solutionsmentioning

confidence: 99%

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

Hubbard¹,

Rynders²

1947

“…Electrodes from glasses of 76 percent and 78 percent of 8i02 survived for 24 hours, whereas electrodes from the other glasses having smaller percentages of 8i02 fail ed after much shorter service. (1)(/)(/)-. In iight of the present results, it seems desirable to rein terpret the pH response data previously presented for a limited series of K20-8i02 glasses [16]. Upon calculating the pH response for these "old" glasses between pH 4.1 and 8.2 (table 2), and plotting the values obtained against the hygroscopicity, the resulting curve is qualitatively similar to the curve for the present data, (fig .…”

Section: (B) Hygroscopicity a Nd P H Responsesupporting

confidence: 74%

Electrode function (pH-response), hygroscopicity, and chemical durability of soda-potash-silica glasses

Hubbard¹,

Black²,

Holley³

et al. 1951

Self Cite

The pH response, hygroscopicity, and che mi cal durability of a seri es of Na, O-K, O-Si02 glasses have bee n in vestiga ted. The pH responses of electrodes prepared from t hese glasses are in accord wit h similar dat a previously reported for t wo other series of glasses, namely, N a, O-CaO-Si02 and N a20 -PbO-Si02, which showed that (1) glasses of low hygroscopicity produ ce e lectrodes whose pH r espo nse fall below t he t heoretical 59 millivolts per pH a t 25° C predi cted b y t he N ernst equat ion , and (2) electrodes prepared fr om g lasses of poor chemical durabilit y also fail to develop t he full t heoretical voltage.Chemical durability d eterminations b y an interferometer procedure indicate swelling of t he glasses upon exposure to acid buffer s and prononn ced a tta ck in alkaline solutions. p~r ing t he investigat ion som e limi tations of t he interferometer procedure ~or dete rn::llm~g chemical dura bility of glass became eVident. Glasses t hat had ex hibIted direct solut IOn 11l t he a cid pH range were f ound t o show swelling in the early stages of t he exposure. This s woll en layer t hen sloughe d off g iving the appearan ce of a ttack as previou sly lllterpreted.Above 70 percent of Si02, glasses con taining mi xtures of Na20 and K , O have lower h ygroscopicities t han t hose h aving but a single one of t hese oxides.. . . The pH response-hygroscopicity curves appeared to refl ect some of t h e CrI tICal composIt ions of t he phase equilibrium diagram, with glasses in the co mpOSIt IOn ran ge for alpha t ridy mi te yielding electrodes wi t h t he op timu m pH response characteri s tics.

“…Voltage anomalies (errors) of glass electrodes are normally associated with the hygroscopicity [16,19], and changes in the chemical durability [18, 20J of the electrode glass. In the present investigation, as all pH measurements have been confined to a pH range over which little or no voltage departure can be accredited to durability shift of the glass, it seems reasonable to expect that the changes in hydrogen electrode function caused by the various heat treatments of the electrodes might be associated with changes in hygroscopicity.…”

Section: Fi Gu R E 4 Effect Oj the Temperatw'e Oj Heat Treatment Onmentioning

confidence: 99%

Effect of annealing and other heat treatments on the pH response of the glass electrode

Hubbard¹,

Rynders²

1948

The effect of annealing and other heat treatments on the pH response of electrodes prepared f,:o m Corning 015 glass has been studied and a comparison made with the accompanying changes in hygroscopicity of the glass. New, unleached electrodes continued to give t he correct pH respon se after being annealed near t he cri tical temperature as indicated by the expan sion curve for Cornin 17 01 5 glass . Electrodes t hat were leached in 0.1 N HCI at SO° C lost much of thei r pH fun ction when given identical heat treatments. The pH respon se of a typical glass electrode, held 10 minutes at 500° C after being leached in 0.1 N Hel for 6 hou rs at SOO C, was reduced from 59 millivolts per pH (the theoretical value at 25° C) to 22 millivolts per pH. A few seconds in hydrofluoric acid solution restored the pH function of these "dead" electrodes, showing that the inhibiting effect was confined to the outer surface of the electrode bulbs. Evidence obtained by the in te rferometer indicated that the t hi ckness of this inhibiting layer was less than 5.SX 10-6 centimeter. Hygroscopicity determination s made on leached samples of t he powdered glass showed t hat the "sorption" power was greatly reduced by heat t reatment, whereas for unleached specimens this property was much less affected. From the evidence obtain ed it seem s reasonable to in terpret the loss in pH funct ion shown by glass electrodes on heat t reatm ent as being due to the formation of a thin non hygroscopic silica-rich layer. T he resulting electrodes behaved in a manner similar to electrode prepared from glasses of low h yg roscopicity.