摘要:

Accelerated tests for antioxidant activity are described which depend on the protection of vitamin A concentrates (in ethylene dichloride solution) against ultraviolet irradiation, and on the protection of carotene (in mineral oil solution) against heat and aeration. The protection of vitamin A was influenced by light-filtering effects; the carotene method appeared to be more generally useful. The stabilizing power of wheat-germ oil for both solutions of Vitamin A and carotene against light is partly due to a screening effect by pigments. Some of the protection is also due to other components of the wheat-germ oil, but it is not known whether these function as stabilizers against light according to the usual theories of antioxidant action. Light-accelerated decomposition of vitamin A and carotene appeared more suitable for special tests than for general evaluation of antioxidants; stability experiments in the absence of light gave a more generally applicable picture of antioxidant activity.

ISSN:1923-4287    

DOI:10.1139/cjr50f-013

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

Experimental results are given for trials of the C.F.R. engine at 900 r.p.m. and 12: 1 C.R. on Toronto town gas alone and with an addition of hydrogen sulphide. The sulphide led to such severe preignition that measurements of power were impossible except for very weak or very rich mixtures. The former included the 50% weak mixture for which thermal efficiency is a maximum. The sulphide was then of beneficial effect, a maximum value of 44% for indicated thermal efficiency being obtained as compared to a maximum of 42.5% without it. The experimental results are interpreted in the light of combustion tube experiments showing that hydrogen in mixtures with air is not ignited by red hot surfaces on which it is oxidized with sufficient rapidity to steam, but that ignition occurs at relatively low temperatures if the surface reaction is inhibited by hydrogen sulphide. The conclusion is that fuel gases containing hydrogen in large proportion can be used for full power engine operation at compression ratios even higher than 12: 1 if the oxidation of the hydrogen in part to steam, on the hot surfaces in the combustion chamber, is not inhibited by the poisoning effect of the hydrogen sulphide commonly present in the gases.

ISSN:1923-4287    

DOI:10.1139/cjr50f-014

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

When using gaseous fuels for the C.F.R. engine, the lubricating oil decomposed to finely divided carbon when the gas was hydrogen and optimum spark advance nearly zero. When town gas was used, optimum spark advance varied from 85 to 15 degrees of crank angle, according to mixture strength, and the lubricant yielded carbon of the hard adherent graphitic variety. When using an L head engine having a combustion chamber with a large surface-to-volume ratio and with the spark plug so placed that optimum spark advance for town gas was approximately half that required with the C.F.R. engine, no appreciable carbon deposit of any variety was obtained. Conditions were therefore such that knocking combustion observed on adding finely divided carbon to the gas–air mixture was not caused to any appreciable degree by carbon derived from the lubricant. It was then found on adding carbon, as graphite dust, at a measured rate to the entering mixture, that approximately 0.3 mgm. in the end gas caused a knock intensity of the degree required to reduce brake horsepower by from 10 to 14%.

ISSN:1923-4287    

DOI:10.1139/cjr50f-015

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

A survey is given of recent work on noise suppression in triode amplifier stages. A theory can be developed, in which the noise factor is expressed in terms of four complex quantitiesg0,g1,i0, andi1.g0andg1are the complex transconductances in the cathode lead and in the anode lead, respectively;i0andi1are the Fourier components of the noise currents flowing in these leads, respectively. These quantities are complex owing to transit time effects. The theory is developed under the assumption thati0andi1are completely correlated. Experiments indicate that no complete noise suppression is possible if there is no feedback; according to the above theory this means that the real part of (g0 − g1i0/i1) is positive. Knol and Versnel showed recently that a complete noise suppression can always be obtained under the above assumption of complete correlation if a suitable amount of external feedback is applied. With the help of the above theory it is shown, however, that the available power gain under those circumstances is less than unity.

ISSN:1923-4287    

DOI:10.1139/cjr50f-016

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

A survey of the heavy metal content of canned shellfish and crustaceans sold on the Canadian market has been made. With the exception of one sample of clams having 5 p.p.m. of lead, one sample of lobster having 13 p.p.m. of lead and, one sample of lobster having 7 p.p.m. of arsenic, of the 120 samples analyzed the values found were not significantly above the limits established for the heavy metal content of foods.

ISSN:1923-4287    

DOI:10.1139/cjr50f-017

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The amount of carrageenin extracted from a sample of rinsedChondrus crispusincreased linearly with temperature of extraction up to 100 °C., and more slowly thereafter up to 110 °C. Increasing the temperature to 125 °C. had no further effect on the yield. Heat treating carrageen or replacing the calcium and potassium in it with sodium increased the yield of carrageenin at lower temperatures.The viscosity of carrageenin extracts obtained at different; temperatures increased and the concentration required to increase the viscosity of milk to 15 centistokes (i.e., the "suspending concentration" for cocoa in milk) decreased with temperature of extraction up to 60 °C. Above this temperature the viscosity decreased and the suspending concentration increased. The increase in viscosity is attributed to the extraction of higher polymers of carrageenin with increased temperature; the decrease, to heat depolymerization during extraction. Neither the solubility nor the fractionation studies gave any indication of chemically distinct carrageenin components. The essential difference between carrageenin that was most effective if incorporated with cold milk and carrageenin that was most effective if incorporated with hot milk was that the former was of high suspending concentration. A method of evaluating carrageen which gives soluble carrageenin divided by suspending concentration was tested but the results were sensitive to variations among samples of milk. When the same milk was used, the correlation coefficient between the concentration required to give viscosities of 15 centistokes in milk and in 0.05 Nsodium chloride for 12 samples was.93. Viscosity in 0.05 Nsodium chloride is preferred for evaluation of carrageen.

ISSN:1923-4287    

DOI:10.1139/cjr50f-018

出版商:NRC Research Press    

年代:1950

数据来源: NRC

摘要:

The ability of soaps to prevent the deposition of carbon black and other materials on fabric during the detergent process has been investigated. In general the suspending power of the soap solutions studied increased rapidly with increasing soap concentration, and reached a maximum at a relatively low concentration. At higher concentrations the suspending power either remained constant or decreased slightly. With carbonaceous soils the indicated suspending power for a given soap increased, in general, with increasing particle size and decreasing "structure" of the carbon. With various soiling materials differences were encountered, not only in the magnitude of the indicated suspending power, but also in the form of the curve obtained on plotting suspending power vs. soap concentration. As measured by one type of carbon black (Standard Micronex) only minor differences were found between suspending powers of sodium myristate, palmitate, and stearate, all of which were higher than that of the laurate. Increasing temperatures caused a decrease in the suspending power of the lower chain length soaps (C12, C14) and an increase in the suspending power of the longer chain soaps (C16, C18). The suspending power of sodium oleate was essentially unchanged by temperature variations over the range 25–80 °C.

ISSN:1923-4287    

DOI:10.1139/cjr50f-019

出版商:NRC Research Press    

年代:1950

数据来源: NRC