Dry Collodion Research Articles

„Argint şi soare”. Originile fotografiei prin evoluții tehnice între 1800 şi 1900 / “Silver and sunshine”. The Origins of Photography by means of Processes between 1800 and 1900

„Argint şi soare”. Originile fotografiei prin evoluții tehnice între 1800 şi 1900 / “Silver and sunshine”. The Origins of Photography by means of Processes between 1800 and 1900

THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

1. The electrochemical behavior ("activity") of collodion membranes depends upon acidic, dissociable groups located in the interstices of the membranes. The active groups can be determined by base exchange measurements. High base exchange capacity is always found with preparations of great "electrochemical activity;" medium and low base exchange capacities occur with electrochemically active as well as with inactive preparations. The observed base exchange capacity is determined by two factors: the inherent acidity of the collodion (its mean equivalent weight) and the submicroscopic micellar structure of the collodion. A comparison of the base exchange capacity of various collodion preparations and their inherent acidities therefore allows certain conclusions to be drawn concerning the relative availability of the micellar surfaces in the different preparations. 2. The inherent acidity of various collodion preparations, their "acid number," was determined by electrometric titration. Collodion in the acidic state, i.e. after exchange of all other cations for H(+) ions, was titrated in an organic solvent mixture with alcoholic KOH using a quinhydrone electrode. Details of the experimental procedure are given in the paper. The acid numbers, expressed in milliliters of 0.01 N KOH per gram dry collodion, vary from 1.0 for a highly purified collodion preparation of very low electrochemical activity to 3.3 for a highly oxidized sample of very high activity. Acid numbers of about 1.5 (corresponding to an equivalent weight of about 67,000) are found both with inactive commercial and with fairly active oxidized preparations. The base exchange capacity of the same preparations in the fibrous state as measured after 48 hours of exchange time varies from 0.0013 ml. 0.01 N NaOH per gm. dry collodion for the most inactive preparation up to 0.26 ml. 0.01 N NaOH per gm. for the most active preparation. Thus the acid numbers over the whole range investigated differ only in the ratio of 1:3.3, whereas the base exchange values differ in the range of 1:200. 3. In the inactive preparation only one in 770 acid groups is available for base exchange, in the most active collodion one group in 13; values between these extremes are found with commercial and alcohol purified oxidized preparations. 4. The high base exchange capacity of the electrochemically active preparations is not so much due to their higher acid number as to their more open structure. This difference in structure is ascribed to the presence of a small fraction of low molecular weight material which inhibits normal formation and arrangement of the micelles. 5. Short time base exchange experiments with fibrous collodion indicate that the number of acid groups available for the typical electrochemical membrane functions may be estimated to be about 50 to 1000 times less numerous than those found in the 48 hour base exchange experiments. It is estimated that in membranes prepared even from the most active collodion not more than one in 500 acid groups may be available for the typical membrane functions; with the less active preparations this ratio is estimated to be as high as one in 1,000,000 or more.

THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR

1. Experiments were carried out to decide whether a homogeneous phase (solubility) theory or a micellar-structural theory more adequately describes the behavior of dried collodion membranes with solutions of strong electrolytes. 2. A number of dried collodion membranes were prepared from an electrochemically inactive collodion preparation (state I); the characteristic concentration potentials across them were low, about 30 mv. The membranes were activated by oxidation (state II) to give maximum or nearly maximum concentration potentials (about 50 mv.). The oxidized membranes are dried, dissolved in alcohol-ether, and a new set of dry collodion membranes prepared from this solution (state III). The concentration potentials across these membranes are low. 3. Since the properties of a homogeneous phase should not be influenced by a rearrangement of its constituent particles, the experimental results do not support a homogeneous phase (solubility) theory, but they agree with the predictions of the micellar-structural theory. The characteristic behavior of dried collodion membranes in solutions of strong inorganic electrolytes is therefore due to the micellar character of its interstices.

UNEQUAL DISTRIBUTION OF IONS IN A COLLODION CELL

The properties of dry collodion membranes previously described allow the prediction that cells of these membranes will concentrate solutes under certain conditions. Three such cases have been studied experimentally. 1. A membrane containing thiosulphate and immersed in a solution of iodine concentrates iodide ion. 2. A membrane containing sodium chromate and immersed in mercury chloride concentrates chloride ion. 3. A membrane containing calcium carbonate and immersed in acetic acid concentrates acetate ions.

The Transportation of Carbon Dioxide by Paraffine Oil and Some Other Substances.

In a previous paper1 the use of luminous bacteria as an oxygen indicator was described. Some rough estimates of the passage of oxygen through a number of substances were given, as determined by the length of luminescent columns of bacteria. The properties of several of these substances, notably dry collodion, were of interest and these and some others were selected for further study with reference to carbon dioxide. In this case the time in hours required for one atmosphere of carbon dioxide to decolorize 1 cm. of phenolphthalein in NaOH agar is used for comparison. It is clearly recognized that this is not a quantitative method for the study of diffusion as there is a concentration gradient of carbon dioxide in the colorless portion of the phenolphthalein as well as through the membrane closing the tube. Nevertheless, it makes a very striking demonstration for class use and does give a qualitative expression for the passage of carbon dioxide. The proper methods of quantitative study may be found in the p...

Comparison of Resistance Changes in Collodion Membranes and Cells.

Most conductors, both metallic and electrolytic, follow Ohm's law, the current being proportional to the applied potential, and the resistance a constant (with exceptions in the case of temperature rise or dielectric breakdown). In the large cells of Valonia and Nitella, however, the resistance becomes higher with increase of potential from 25 to 150 millivolts, under some conditions.1This discovery led to a search for a non-living model of this phenomenon and such has been found in dry collodion films, thinner than those used by Michaelis,2 and Northrop;3 thicker membranes show the effect in smaller degree. When direct current is passed across such thin films separating 2 solutions of good conductivity, the resistance is found to vary with the applied potential. With sea water on both sides, the resistance is a minimum below 100 millivolts, and may rise as much as 100% when the potential is increased to 3 or 4 volts. Above this voltage irregular results are obtained.The course of the resistance rise is v...

THE PERMEABILITY OF DRY COLLODION MEMBRANES. II

The rate of penetration and the solubility of H, O, N, NH(3), H(2)O, HCl gas, CO(2), formic, acetic, chloracetic, dichloracetic acid, glycerol, phenol and mercury bichloride in dry collodion membranes have been measured. The rate of penetration of H and CO(2) is the same whether the membrane and gas are dry or whether the membrane is immersed in water. The solubility of CO(2), acetic acid, phenol and water in collodion is completely reversible and is proportional to the concentration (or vapor pressure) in low concentrations and independent of the surface of the collodion. The size of the pores has been calculated from the vapor pressure of water in the collodion and from the rate of flow of water through the membrane. The results do not agree and are not consistent with the observed rates of penetration. The relative rates of penetration of the gases bear no relation to the density of the gas. When the results are corrected for the solubility of the substances in the collodion and expressed as the diffusion coefficient in collodion they show that the diffusion coefficient increases rapidly as the molecular weight decreases.

CONTRIBUTION TO THE THEORY OF PERMEABILITY OF MEMBRANES FOR ELECTROLYTES

From experiments on such membranes as apple skin, parchment paper membrane, and a membrane of completely dry collodion, results have been obtained which could be interpreted by the assumption that these membranes are less permeable for anions than for cations. In parchment paper there is only a relative diminution of the mobility of the anions, in the apple skin and in the dry collodion membrane there is practically no permeability for anions at all. The theory is developed which explains how the decrease or complete lack of mobility of anions influences the electromotive effects of the membrane and the diffusibility of electrolytes across a membrane. The results of the theory are compared with the experimental results. In membranes impermeable for anions the permeability for cations gives the same order of cations as for the mobilities in a free aqueous solution. But the differences of the mobilities are enormously magnified, e.g. the mobilities of H(*) and Li(*), which are in the proportion of about 1:10 in aqueous solution, are in proportion of about 1:900 in the collodion membrane. The general cause for the retardation of ionic mobility within the membrane may be supposed to be the increased friction of the water envelope dragged along by the ion in the capillary canals of the membrane. The difference of the effect on the cations and on the anions may be attributed to the electric charge of the walls of the canals.

II. On reversed photographs of the solar spectrum beyond the red, obtained on a collodion plate, in a letter to Prof. Stokes. By Captain J. Waterhouse, Assistant Surveyor General of India. Communicated by Professor Stokes

Mv deae Sir,—I have the pleasure to send you, by Overland Parcel Post, for presentation to the Royal Society, two photographs on glass of the solar spectrum, showing the extreme red rays below A, obtained on a dry collodion plate prepared with bromide of silver stained with a blue and exposed to diffused daylight for a moment before being placed a the camera to receive the image of the spectrum. I also send another late, also a dry bromide plate, stained with the same blue dye, and prepared at the same time and in the same manner as the other plates, but not exposed to light and quite free from fog; and you will observe hat on this there is no trace of the reversed action in the red rays, and that the direct action only extends slightly below C. This power of the red rays of the spectrum to neutralize the action of white light on sensitive daguerreotype plates was frequently noticed by Sir J. Herschel, Draper, Fizeau, Claudet, and other daguerreotypists about thirty years ago, but, so far as I can ascertain, it has never been observed on collodion plates. As collodion has so many advantages over the daguerreotype, it seems probable that this new extension of an old principle may have an important practical application in spectroscopic photography, particularly for the mapping of a part of the spectrum in which eye-observations can only be made with difficulty and under favourable circumstances.

Long's dry collodion process

Journal Article Long's dry collodion process Get access Notes and Queries, Volume s2-IV, Issue 96, 31 October 1857, Page 356, https://doi.org/10.1093/nq/s2-IV.96.356a Published: 31 October 1857

Barnes' Dry collodion process

Barnes' Dry collodion process