scholarly journals VIII. The variations of electromotive force of cells consisting of certain metals, platinum, and nitric acid

1891 ◽  
Vol 182 ◽  
pp. 319-339 ◽  
Keyword(s):  
Nitric Acid ◽  
Nitrous Acid ◽  
Electromotive Force ◽  
Chemical Change ◽  
Division Of Labour ◽  
Contact Theory ◽  
Necessary Condition ◽  
Continuous Formation ◽  
High Degree ◽  
Voltaic Cell

The experiments described by one of us in another paper have established that the necessary condition for the chemical reactions between nitric acid and the metals copper, mercury, and bismuth, is the presence and continuous formation of nitrous acid. These results confirm the previous observations of Russell in the case of the metal silver. Further, it has been shown that when these metals are introduced into purified nitric acid, no apparent change takes place at first, but after some time gas bubbles are seen to rise from the surface of the metal, and the liquid then contains an amount of nitrous acid which can be detected by the more delicate reagents. The amount of this acid increases up to a maximum and constant point, while concomitantly the amount of metal dissolved per unit of time equally increases to a maximum and constant value. It seemed, therefore, desirable to ascertain if these phenomena determined by the balance are correlated with any alteration of electromotive force. To avoid any misunderstanding, however, it would be advisable at the outset to state that this paper is separated from that of one of us “On the Condition of Chemical Change between certain Metals and Nitric Acid,” rather on account of division of labour than of difference of subject. The idea of measuring the electromotive force of cells consisting of platinum, certain metals, and nitric acid occurred to the latter of us, while the apparatus and method of measurement finally adopted are due solely to the former. Previous Investigations . Many years ago Faraday pointed out that neither nitrogen peroxide nor nitric acid are conductors when pure, but that the addition of water to the former, or of nitrous acid to the latter, produces the property of conductivity “in a very high degree among electrolytes.” Thus the presence of nitrous acid is the necessary condition that nitric acid should become an electrolyte. Again, Faraday proved that the electric position of certain pairs of metals in nitric acid is varied according to the conditions of concentration and temperature; in fact, experiments on this point were considered by him to be of especial importance in confirming the chemical and disproving the contact theory of the voltaic cell.

I. Contact theory of voltaic action. Parts I and II

1878 ◽  
Vol 27 (185-189) ◽  
pp. 196-238 ◽  
Keyword(s):  
Electromotive Force ◽  
Zinc Sulphate ◽  
Copper Plate ◽  
Contact Theory ◽  
Metallic Contact ◽  
A Value ◽  
A Cell ◽  
The Difference ◽  
Voltaic Cell

The contact theory of voltaic action seems to have undergone no development since the date of Sir W. Thomson’s experiment, which consisted in connecting a plate of zinc and a plate of copper by means, of a drop of water, when it was found that the metals were brought to the same electric potential, although when metallically connected they were at different potentials. He believed that any electrolyte would behave in exactly the same way as the water of his experiment, equalizing the potentials of any two metals connected by it. The electromotive force of a simple cell, ought, in accordance with the theory, to be equal to the difference of potentials between zinc and copper in; contact. A test founded on this deduction was very difficult to apply, because there was no exact determination of the difference of potential of zinc and copper in contact, Sir W. Thomson, in his experiment, having really measured the difference of potential between air at the surface of a zinc plate, and air at the surface of a copper plate. In the absence of this test, the equality of the electromotive forces of simple cells in which zinc and copper are the metals (the liquids being water, dilute sulphuric acid, and sulphate of zinc) was held as a proof of the theory. Now it is known that when two pieces of the same metal are dipped into any two liquids, which are diffusing into one another, a difference of potentials is established between the metals, and the electromotive force of a cell of this kind can in no way depend on a difference of potentials due to metallic contact. So that although in such a cell there is an action which is somewhat the same as the action in a simple voltaic cell, the theory took no account of it whatever. In fact, the explanation of voltaic action given in the latest treatises on electricity is felt to be incomplete, even by the writers of such treatises, and the present investigation has been entered upon in consequence. Sir W. Thomson’s result, and our own experiments lead us to magine that when zinc and copper are immersed in water there are three successive states to be noticed:—At the instant of immersion the zinc and copper may be reduced to the same potential, so that the electromotive force of the voltaic cell E is equal to the difference of potential ZC — between zinc and copper in contact; the zinc now becomes negative to the copper, so that E reaches a limit which is greater than ZC — ; lastly, if a current passes, polarization occurs and the zinc becomes gradually less negative to the copper, E diminishing, therefore, from its maximum value# But when a saturated solution of zinc sulphate is employed instead of water, the first state, if it exists at all, exists for so short a time that practically, zinc and copper in zinc sulphate are never at the same potential. Thus (see Table X ) when care is taken to keep the zinc and copper in a water cell well insulated from one another, E is found to increase from a value very little greater than ZC — , the electromotive force of contact of zinc and copper, to a limit, but in a zinc sulphate cell no such great increase is observed.

scholarly journals IV. The conditions of chemical change between nitric acid and certain metals

1891 ◽  
Vol 48 (292-295) ◽  
pp. 458-459 ◽  
Keyword(s):  
Nitric Oxide ◽  
Hydrogen Peroxide ◽  
Nitric Acid ◽  
Potassium Permanganate ◽  
Nitrous Acid ◽  
Chemical Change ◽  
Potassium Chlorate ◽  
Cent Concentration ◽  
Preliminary Communication ◽  
A Current

This paper is in continuation of a preliminary communication on the same subject; the main points contained in it are as follows: I. The metals copper, mercury, and bismuth do not dissolve in nitric acid of about 30 per cent, concentration (the acid commonly employed for the preparation of nitric oxide gas) and heated to a temperature of 30ºC., provided that nitrous acid is neither present initially nor formed subsequently. To prevent this, it is nocessary in the cases of copper and bismuth to add a small quantity of some oxidising substance, such as hydrogen peroxide or potassium chlorate, or, as less efficacious, potassium permanganate, or to pass a current of air or, lastly, such a substance as urea, which destroys the nitrous acid by its interaction.

scholarly journals V. The variations of electromotive force of cells consisting of certain metals, platinum, and nitric acid

1891 ◽  
Vol 48 (292-295) ◽  
pp. 460-460
Keyword(s):  
Nitric Acid ◽  
Nitrous Acid ◽  
Electromotive Force ◽  
Initial Value ◽  
Final Value ◽  
Maximum Value ◽  
Remarkable Degree ◽  
A Cell ◽  
Metallic Strip

The description of the apparatus, the capillary electrometer, and the method of working are given fully in the paper. The following conclusions are drawn from the results of the experiments:— I. When the metals copper, silver, bismuth, and mercury are introduced into purified nitric acid of different degrees of concentration, and a couple made with platinum, the electromotive force of such a cell increases considerably until it reaches a constant and (in most cases) a maximum value. The rise of E. M. F. is attributed to the production of nitrous acid by the decomposition of the nitric acid, and the final value is considered to be due to the former acid only, while the initial value is due for the most part to the latter acid, though it is affected to a remarkable degree by the amount of impurity of nitrous acid, either initially present, or produced by minute and unavoidable uncleanliness of the metallic strip and the containing vessel.

scholarly journals Cultural diversity and wisdom of crowds are mutually beneficial and evolutionarily stable

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benoît de Courson ◽  
Léo Fitouchi ◽  
Jean-Philippe Bouchaud ◽  
Michael Benzaquen
Keyword(s):  
Social Learning ◽  
Information Seeking ◽  
Information Quality ◽  
Evolutionary Model ◽  
Division Of Labour ◽  
Necessary Condition ◽  
Wisdom Of Crowds ◽  
Human Species ◽  
Evolutionarily Stable ◽  
Individual Information

AbstractThe ability to learn from others (social learning) is often deemed a cause of human species success. But if social learning is indeed more efficient (whether less costly or more accurate) than individual learning, it raises the question of why would anyone engage in individual information seeking, which is a necessary condition for social learning’s efficacy. We propose an evolutionary model solving this paradox, provided agents (i) aim not only at information quality but also vie for audience and prestige, and (ii) do not only value accuracy but also reward originality—allowing them to alleviate herding effects. We find that under some conditions (large enough success rate of informed agents and intermediate taste for popularity), both social learning’s higher accuracy and the taste for original opinions are evolutionarily-stable, within a mutually beneficial division of labour-like equilibrium. When such conditions are not met, the system most often converges towards mutually detrimental equilibria.

scholarly journals IX. The electric conductivity of nitric acid

1898 ◽  
Vol 191 ◽  
pp. 365-398 ◽  
Keyword(s):  
Nitric Acid ◽  
Physical Properties ◽  
Nitrous Acid ◽  
Internal Resistance ◽  
The Other ◽  
Reasonable Degree ◽  
Mineral Acids ◽  
Artificial Illumination ◽  
The Subject ◽  
Deep Green

Of the commoner mineral acids the chemical changes of Nitric Acid, from their evident complexity, have formed the subject of numerous memoirs, while those of sulphuric acid, from their assumed simplicity, have been to some degree neglected; on the other hand, the physical properties of the latter have been studied with considerable elaboration, while those of the former have been passed over, doubtless on account of the corrosive nature of the acid and the difficulty of preparing and preserving it in a reasonable degree of purity. Further, with certain exceptions, the alterations in physical properties induced by the products of reduction, be they nitrogen peroxide or nitrous acid, either singly or conjointly, have attracted but little attention, though it is a common matter of observation that the current intensity of a Grove’s or other cell containing nitric acid remains constant, even though the fuming acid, originally colourless or red, has become of a deep green tint. It is more than probable that of the factors of Ohm’s law, both the E. M. F. and internal resistance are continually varying. At the earliest stages of the enquiry it was found that the passage of a few bubbles of nitric oxide gas into a considerable volume of nitric acid produced an alteration of one percent, in the resistance, and the same result could be effected to a less degree by exposure to sunlight, and to a still less degree by exposure to artificial illumination. Therefore, we determined to investigate the alterations of conductivity produced by changes of concentration and temperature in samples of acid purified with necessary precautions, more especially as former workers upon the subject have either used samples of acid confessedly impure, or have been silent as to any method of purification, or have adopted no special care in dealing with a substance so susceptible of polarisation.

scholarly journals INVESTIGATION OF DECOMPOSITION OF PHOSPHATE RAW MATERIALS IN THE PRESENCE OF PEAT USING PHOSPHORIC ACID

2020 ◽  
Vol 55 ◽  
pp. 10-15
Author(s):  
Katerina I. Panova ◽  
◽  
Nicolay N. Pravdin ◽  
Аnatoliy О. Kiryanov ◽  
◽  
...  
Keyword(s):  
Nitric Acid ◽  
Phosphoric Acid ◽  
Raw Materials ◽  
Raw Material ◽  
Material Component ◽  
High Degree

In the process of decomposition of phosphate raw materials, the dynamics of transformation of its constituent mineral phosphoric components: fluorapatite and its derivatives into available for plants dihydro - and hydroorthophosphates of calcium and the influence of a natural organic activator on it are studied.. The composition of the obtained organomineral products was evaluated. The questions of intensification of processing of phosphorite in phosphate-peat systems with additional involvement of nitric acid are considered. The possibilities of reducing the amount of acidic reagents to 50% are shown, while guaranteeing a high degree of use of the target raw material component (94%) and the absence of waste.

scholarly journals Evolution of division of labour in mutualistic symbiosis

2020 ◽  
Vol 287 (1930) ◽  
pp. 20200669
Author(s):  
Yu Uchiumi ◽  
Akira Sasaki
Keyword(s):  
Division Of Labour ◽  
Living Alone ◽  
Mutualistic Symbiosis ◽  
Obligate Mutualism ◽  
High Degree

Mutualistic symbiosis can be regarded as interspecific division of labour, which can improve the productivity of metabolites and services but deteriorate the ability to live without partners. Interestingly, even in environmentally acquired symbiosis, involved species often rely exclusively on the partners despite the lethal risk of missing partners. To examine this paradoxical evolution, we explored the coevolutionary dynamics in symbiotic species for the amount of investment in producing their essential metabolites, which symbiotic species can share. Our study has shown that, even if obtaining partners is difficult, ‘perfect division of labour’ (PDL) can be maintained evolutionarily, where each species perfectly specializes in producing one of the essential metabolites so that every member entirely depends on the others for survival, i.e. in exchange for losing the ability of living alone. Moreover, the coevolutionary dynamics shows multistability with other states including a state without any specialization. It can cause evolutionary hysteresis: once PDL has been achieved evolutionarily when obtaining partners was relatively easy, it is not reverted even if obtaining partners becomes difficult later. Our study suggests that obligate mutualism with a high degree of mutual specialization can evolve and be maintained easier than previously thought.

scholarly journals Attitudes Towards Statistics in Secondary Education: Findings from fsQCA

Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 804 ◽  
Author(s):  
Ángel Peiró-Signes ◽  
Óscar Trull ◽  
Marival Segarra-Oña ◽  
J. Carlos García-Díaz
Keyword(s):  
Secondary Education ◽  
Secondary School ◽  
Secondary School Students ◽  
Linear Models ◽  
Qualitative Comparative Analysis ◽  
Necessary Condition ◽  
School Students ◽  
Self Confidence ◽  
Attitudes Toward Statistics ◽  
High Degree

Students report a high degree of anxiety and reduced self-confidence when facing statistical subjects, especially in secondary education. This anxiety turns into poor academic performance. Most studies have used linear models for studying the interrelation between different attitudes and proving their impact on performance or related variables. This study uses a different approach to explain and better understand the causal patterns of factors stimulating lower levels of anxiety in students when facing statistics in secondary education. We employed the Multi-factorial Scale of Attitudes Toward Statistics (MSATS) and fuzzy-set qualitative comparative analysis (fsQCA) on a sample of 95 secondary school students in Spain. We identified the recipes or causal combination of factors, leading to low and high levels of anxiety. The results indicate that self-confidence and motivation are important factors in these recipes, but there is no single necessary condition that ensures lower levels of anxiety.

Friendship potential: Conversation-based programming and immigrant integration

2017 ◽  
Vol 51 (3) ◽  
pp. 670-688 ◽  
Author(s):  
Jamie Johnston
Keyword(s):  
Social Networks ◽  
Participant Observation ◽  
Immigrant Integration ◽  
Contact Theory ◽  
High Degree ◽  
Case Based

Using Contact Theory as a lens, this article presents the results of a case-based study in Norway on language cafes and integration. The methodology includes participant observation and questionnaires for both the programmes’ participants and volunteers. The results show that the programming reduces intergroup prejudice by fostering the following four processes: learning about the out-group, changing behaviour, generating affective ties, and in-group reappraisal, as well as offering a high degree of friendship potential. Thus, the programming supports the expansion of social networks across intercultural lines and, thereby, facilitates integration.

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