No abstract

The operational pH numbers for solutions in alcohol-water solvents obtained from the e.m.f. of the cell with hydrogen (or glass) electrode, salt bridge, and calomel reference electrode, standardized with aqueous buffer standards, are subject to no simple interpretation. Because of the indeterminate potential at the junction solution X (alcohol-HaO) j KC1 bridge (aq.), they do not lie on a conventional scale of hydrogen ion activity referred either to the aqueous standard state ( ) or to the standard state in the alcoholic medium (pon*)• Values of £¡ + log m7ci (where E¡ is the liquid-junction potential expressed in pH units and "7ci is the primary medium effect of chloride ion) -were found to be as constant for different buffer solutions in alcoholic solvents of fixed composition as for the strictly aqueous medium. Inasmuch as m7ci at a given temperature is dependent only on solvent composition, the liquid-junction potential must therefore also be nearly constant for a given solvent medium. Correction terms E¡ -log myn = 5 have been calculated, and it is shown that pHclosely approximates pan* under optimum conditions of measurement. An operational scale of pH* (which is related to * in the same way that pH is related to pan) is described. Values of pan* were obtained for 12 solutions in methanol-water solvents (0 to 68.1 wt. % MeOH) and for 3 solutions in ethanol-water solvents (0 to 100% EtOH).chosen for measurement of the difference pH*(X) -pH*(S).

Schematic of NBS gas analysis system.

J -' A b uff er sol ution containing p otassiu m dihydrogen p hosphate (0.008695 m olal) an d d isodiu m h ydrogen phosphate (0.03043 molal) is p roposed as a pH standard for t he p hysiologically important r a nge, pH 7 to 8. The proposed stand ard solut ion is prepared by dissol ving 1.179 g (air weight ) of po tassium dihyd rogen phosp hate and '1.3 03 g (a ir weight) j of disodium h ydrogen phosphate i n a mmonia-free water a nd di lut in g to 1 liter at 25°C . The ionic strength is 0.1.Standa rd pH val ues (pH .) were assign ed t o t his r eference solution at tem peratures from 0 to 50 °C by mea ns of emf m easuremen ts of h ydrogen-sil ve r chlorid e cells wit hou t liquid jun ction. Th e acti vity coeffi cient of chl ori de ion, upon whi ch t he assignment of pH. d epends, was eval uated by means of a r ece nt ly proposed convention. By t his m eans, '-standard values precise to ± 0.001 u ni t co uld be deri ved from t he emf data. At 25°C pH .is 7.4 14 , a nd at 38 °C it is 7.382. The operatio na l consistency of t hese standard values wit h t hose for t he 0.025-m equ imo lal p hosp hate bu ff er (one of t he KBS p ri mar y s ta ndards) was d em o nst rated . I . IntroductionThe acid-ba se beh avior of blood and o ther physiological fluids h as b een widely s Ludied in recen t year s in m edical and biological la boratories in an a t temp t to discover t be relationships that exist among physiological fun ctions, pathological condi tions, and pH.Many of these fluids are well buffered, and t he detection of any sys tem atic variation of pH with physiological condi tion would therefo re b e exp ected to r equire precise measuring equipmen t. Such equipmen t is readily available commer cially in t he form of the n ewer highly-sensitive pH mcter s with a gl ass electrode.Experience has shown that, wi th the exer cise of care, the inves tiga tor or clinician can ob tain glasselectrode pH valu es, for reduced blood and other body fluids, th at agr ee wi thin ± 0.01 uni t wi th pH numbers obtained by m eans of the hydrogen electrode [1]. J Th e high degr ee of sta bili ty in these biological systems and in the m easuring appara tus sugges ts that blood pH m easurem en ts with a precision of 0.00 5 unit (or even 0.001 unit) could profitably b e m ade. M eaningful comparisons of highly precise resul ts of different laboratories could th en b e m ade, provided that a sui table referen ce standard wer e available.Unfortunately, useful comparisons of pH data , quo ted to 0.001 uni t, from differen t sources h ave in general b een impossible. The difficulty can be a t tributed to the fact t ha t in all of the m a.jor conventions definin g pH [2], a 110n thermod yn amic conven tion concerning single-ion s,ctivi ty coeffi cien ts is by n ecessity adop ted . A t th e present time no single convention fo1' definin g a n ionic activity is widely accepted . Al th ough the conven tions used her etofore to estimat e single-ion activity coeffi cien ts are " reasonable" and yield pH numbers consisten t 1 :Figures in brackets...

The literature on polyethylenes has been reviewed with an emphasis on the identification of gaseous products generated under various thermal decomposition conditions and the toxicity of those products. This review is limited to publications in English through 1984. The analytical chemical studies of the thermal decomposition products generated under vacuum, inert and oxidative experimental conditions are described. In oxidative atmosphere, which most closely simulate real fire conditions, carbon monoxide (CO) was found to be the predominant toxicant. Acrolein was another toxicant often noted in these reviewed studies. More acrolein was generated under non‐flaming than under flaming conditions. Results from seven different test procedures were considered in assessing the acute inhalation toxicity of combustion products from various polyethylene formulations. The combustion products generated from the polyethylenes studied in the non‐flaming mode appeared to be slightly more toxic than those produced in the flaming mode. In the non‐flaming mode the LC50 values ranged from 5 to 75 mg l−1. In the flaming mode the LC50 values ranged from 31 to 51 mg l−1. The toxicity of the degradation products of polyethylenes appears to be similar to that found for other common materials designed for the same end uses.