Tetravalent Anion Research Articles

Brush assisted layer-by-layer assembled lignin/polyelectrolyte membrane

A lignin/polyelectrolyte membrane was facilely fabricated by a novel brush assisted layer-by-layer (LBL) assembly approach using poly(allylamine hydrochloride) as a polycation, sodium lignin sulfonate (SLS) as a polyanion, and glutaraldehyde as a crosslinker. This approach favors the quick formation of an effective separation layer compared to the classical static LBL assembly. The obtained membrane exhibits high rejection to trivalent and tetravalent anion salts (>90%), along with high permeate flux (up to 66.3 L m−2h−1). The ultrathin separation layer (15 nm) and excellent hydrophilicity favor the enhancement of the permeate flux. The abundant hydrophilic groups of the outermost SLS layer and negatively charged surface endow the membrane with good fouling resistance to bull serum albumin. The membrane also shows good stability on the separation performance.

Development and evaluation of an improved quantitative loop-mediated isothermal amplification method for rapid detection of Morganella morganii

A point-of-care diagnostic kit was developed for detection of Morganella morganii using optimized loop-mediated isothermal amplification (LAMP) technique within less than an hour. In that regard, dimethyl sulfoxide (DMSO) was utilized together with betaine and all variables were optimized to improve the efficiency of the method. Moreover, surface presentation of antigens protein was targeted and six unique primers were designed. Endpoint turbidity analysis was performed at 550 nm to measure the tetravalent anion (pyrophosphate) released during the reaction. The specificity of the method was evaluated using nine closely related bacterial species as well as its sensitivity. It was shown that the improved LAMP assay could significantly distinguish M. morganii from other bacteria while the sensitivity was determined to be 0.2 CFU mL-1.

Metalloporphyrin-Based Porous Coordination Polymers: Synthesis, Served as Heterogenous Catalysts and Dye Scavengers

Six metalloporphyrin-based porous coordination polymers, MnII(TCP)-MnII (CP1), FeIII(TCP)-FeIII (CP2), CoII(TCP)-CoII (CP3), NiII(TCP)-NiII (CP4), CuII(TCP)-CuII (CP5) and ZnII(TCP)-ZnII (CP6), (TCP = 5,10,15,20-tetra(4-(phenoxy-4-yl)butanoic acid)porphyrin tetravalent anion) were prepared and characterized. CP1, CP2, CP3, CP4 and CP6 are amorphous aggregation supported by SEM, TEM and powder XRD. CP5 is a small particles aggregation with lower crystallinity. These coordination polymers exhibit effective dye scavenging and catalytic activities toward the oxidation of alkylbenzene to ketones, and can be reused by filtration with slight decreasing of catalytic activities.

Insights into the Formation and Structures of Molecular Gels by Diimidazolium Salt Gelators in Ionic Liquids or "Normal" Solvents.

Insights are provided into the properties of molecular gels formed by diimidazolium salts both in "normal" solvents and ionic liquids. These materials can be interesting for applications in green and sustainable chemistry in which ionic liquids play a significant role, like catalysis and energy. In particular, two positional isomers of a diimidazolium cation have been examined with a wide range of anions for their ability to form gel phases. In particular, di-, tri-, and tetravalent anions bearing aliphatic or aromatic spacers were paired with the divalent cations. The properties of the organo- and ionogels formed have been analyzed by means of several different techniques, including calorimetry, rheology, resonance light scattering, UV/Vis absorption, polarizing optical microscopy, and powder X-ray diffraction measurements. The investigations performed enabled us to obtain a wide range of conductive materials characterized by a high thermal stability and a low corrosiveness of the gelator (organogels) or of both gelator and solvent (ionogels). The information gained should be useful in the broader quest to identify and promote their applications.

Supramolecular assembly of binuclear complexes of rare earth elements with polyaminopolycarboxylate and dodecatungstosilicate

Rare earth elements (RE), polyaminopolycarboxylate and dodecatungstosilicate had self-assembled into four new supramolecular salts [RE2(H2CyDTA)2(H2O)12][H2SiW12O40]·nH2O, RE=Y, n=14 (1); RE=Sm (2), Eu (3), n=17; RE=Er, n=16 (4), CyDTA=trans-cyclohexanediaminotetraacetate tetravalent anion, in aqueous solution and they were characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. Eight-coordinated RE ion accepts two carboxyl oxygen atoms from two CyDTA and the CyDTA bridges two RE ions, forming a binuclear complex cation, [RE2(H2CyDTA)2(H2O)12]2+. The cations, SiW12O404− anions and lattice water are arranged into three dimensional supramolecular architecture through hydrogen bonds and electrostatic force. Coordination behavior of CyDTA to RE is rather different from that to transition metal ions and different from that without SiW12 presence. Compounds 1 and 2 exhibit ligand-centered luminescence but the intensity decreases; compound 3 shows the characteristic emission of Eu3+ ion and at the same time it retains the ligand-centered luminescence.

Wrapping/unwrapping transition of double-stranded DNA in DNA-nanosphere complexes induced by multivalent anions.

Wrapping and unwrapping behaviors of double-stranded DNA around a positively charged nanosphere in solution are studied by using the coarse-grained molecular dynamics (CGMD) simulation method. When monovalent, divalent and trivalent anions are added to the DNA-nanosphere complex solution, double-stranded DNA binds with a nanosphere owing to strong electrostatic attraction. However, when tetravalent anions are added to the DNA-nanosphere complex solution, local charge inversion is observed for a high anion concentration of tetravalent anions and the double-stranded DNA can be unwrapped from the nanosphere because of the local charge inversion near the nanosphere. Moreover, the helical structure of DNA is damaged when double-stranded DNA wraps around the nanosphere and the helical structure can be rebuilt when the double-stranded DNA unwraps from the nanosphere. This study can help us understand how to control the release of DNA in DNA-nanosphere complexes.

Transformation of a Tetranuclear Copper(II) Complex Bridged by Sugar Phosphates into Nucleotide‐Containing Cu4 Aggregations

AbstractReaction of [Cu4(μ‐OH){μ‐(α‐D‐Glc‐1P)}2(L)4(H2O)2]X3 (1a: L = bpy, X = NO3, α‐D‐Glc‐1P = α‐D‐glucopyranose‐1‐phosphate) with Na2[H2ATP] (ATP = adenosine 5′‐triphosphate) readily afforded the ATP‐bridged tetranuclear copper(II) complex [Cu4(μ‐ATP)2(bpy)4] (3), which was characterized by X‐ray crystallographic analysis to consist of four linearly dispersed {CuII(bpy)}2+ fragments bridged by two triphosphate groups of the ATP tetravalent anions. The sugar and adenine base parts of the ATP moieties are away from the copper(II) centers, but the structure was stabilized by weak intramolecular π–π stacking between the ATP purine ring and two bpy ligands and intermolecular hydrogen bonding between the adenine base pairs. The variable‐temperature magnetic susceptibility of complex 3 exhibited only weak antiferromagnetic couplings between the four linearly dispersed CuII ions. A similar reaction of 1a or 2 (L = phen, X = NO3) with Na2[IMP] (IMP = inosine 5′‐monophosphate) yielded a different type of tetracopper(II) complex formulated as [Cu4{μ‐(IMP‐H)}2(L)4(H2O)4](NO3)2 [L = bpy (5), phen (6)], in which the IMP moieties are deprotonated at the N‐1 position of the nucleobase, forming IMP‐H trianions, and four {Cu(bpy)(H2O)}2+ fragments are connected through the N‐1, N‐7, and O‐6 atoms of the nucleobase and the monodentate 5′‐phosphate group. Reaction of 1b (L = bpy, X = Cl) with Na2[UMP] (UMP = uridine 5′‐monophosphate) resulted in a polymeric compound formulated as {[Cu{μ‐(UMP‐H)}(bpy)(H2O)]2[Cu4(μ‐OH){μ‐(α‐d‐Glc‐1P)}2(bpy)4(H2O)2]Cl}n (7). The N‐3 deprotonated [UMP‐H]3– anions connect {Cu(bpy)(H2O)}2+ fragments through the N‐3 nitrogen atom and the phosphate oxygen atoms to afford C2‐helical coordination polymers and the tetracopper(II) complex cations, [Cu4(μ‐OH){μ‐(α‐d‐Glc‐1P)}2(bpy)4(H2O)2]3+, are incorporated between the polymer chains with a C2‐chiral arrangement of the {Cu4(μ‐OH)(μ‐PO4)2(bpy)4(H2O)2} framework constrained to the Λ‐form through inter‐ and intramolecular stacking interactions between the bpy ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Dinuclear Copper(II) Complexes with {Cu2(μ-hydroxo)bis(μ-carboxylato)}+ Cores and Their Reactions with Sugar Phosphate Esters: A Substrate Binding Model of Fructose-1,6-bisphosphatase

Reactions of CuX2.nH2O with the biscarboxylate ligand XDK (H2XDK = m-xylenediamine bis(Kemp's triacid imide)) in the presence of N-donor auxiliary ligands yielded a series of dicopper(II) complexes, [Cu2(mu-OH)(XDK)(L)2]X (L = N,N,N',N'-tetramethylethylenediamine (tetmen), X = NO3 (1a), Cl (1b); L = N,N,N'-trimethylethylenediamine (tmen), X = NO3 (2a), Cl (2b); L =2,2'-bipyridine (bpy), X = NO3 (3); L = 1,10-phenanthroline (phen), X = NO3 (4); L = 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), X = NO3 (5); L = 4-methyl-1,10-phenanthroline (Mephen), X = NO3 (6)). Complexes 1-6 were characterized by X-ray crystallography (Cu...Cu = 3.1624(6)-3.2910(4) A), and the electrochemical and magnetic properties were also examined. Complexes 3 and 4 readily reacted with diphenyl phosphoric acid (HDPP) or bis(4-nitrophenyl) phosphoric acid (HBNPP) to give [Cu2(mu-phosphate)(XDK)(L)2]NO3 (L = bpy, phosphate = DPP (11); L = phen, phosphate = DPP (12), BNPP (13)), where the phsophate diester bridges the two copper ions in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.268(3)-4.315(1) A). Complexes 4 and 6 with phen and Mephen have proven to be good precursors to accommodate a series of sugar monophosphate esters (Sugar-P) onto the biscarboxylate-bridged dicopper centers, yielding [Cu2(mu-Sugar-P)(XDK)(L)2] (Sugar-P = alpha-D-Glc-1-P (23a and b), D-Glc-6-P (24a and b), D-Man-6-P (25a), D-Fru-6-P (26a and b); L = phen (a), Mephen (b)) and [Cu2(mu-Gly-n-P)(XDK)(Mephen)2] (Gly-n-P = glycerol n-phosphate; n = 2 (21), 3 (22)), where Glc, Man, and Fru are glucose, mannose, and fructose, respectively. The structure of [Cu2(mu-MNPP)(XDK)(phen)2(CH3OH)] (20) was characterized as a reference compound (H2MNPP = 4-nitrophenyl phosphoric acid). Complexes 4 and 6 also reacted with d-fructose 1,6-bisphosphate (D-Fru-1,6-P2) to afford the tetranuclear copper(II) complexes formulated as [Cu4(mu-D-Fru-1,6-P2)(XDK)2(L)4] (L = phen (27a), Mephen (27b)). The detailed structure of 27a was determined by X-ray crystallography to involve two different tetranuclear complexes with alpha- and beta-anomers of D-Fru-1,6-P2, [Cu4(mu-alpha-D-Fru-1,6-P2)(XDK)2(phen)4] and [Cu4(mu-beta-D-Fru-1,6-P2)(XDK)2(phen)4], in which the D-Fru-1,6-P2 tetravalent anion bridges the two [Cu2(XDK)(phen)2]2+ units through the C1 and C6 phosphate groups in a mu-1,3-O,O' bidentate fashion (Cu...Cu = 4.042(2)-4.100(2) A). Notably, the structure with alpha-D-Fru-1,6-P2 demonstrated the presence of a strong hydrogen bond between the C2 hydroxyl group and the C1 phosphate oxygen atom, which may support the previously proposed catalytic mechanism in the active site of fructose-1,6-bisphosphatase.

Preparation and Molecular Structure of Binuclear Nickel (I) Complex Bridged by 1,2,4, 5‐Benzenetetracarboxylato Tetravalent Anion

AbstractThe title complex [(H2O)2(IMI)3Ni(TCB)Ni(IMI)3‐(H2O)2] H2O (TCB = 1,2,4,5‐benzenetetracarboxylato te‐travalent anion; IMI = imidazole) has been prepared by the reaction of Ni(IMI)3(Ac)2 and TCB in aqueous solution. The crystal structure has been determined by single‐crystal X‐ray diffraction method. It crystallizes in the monoclinic system, space group P21/c(# 14), a = 1.2714(4) nm, b = 0.9411 (3) nm, c = 1.5869(4) nm, β= 108.54(2)°, V= 1.8001(9) nm3, Z = 2. The main feature of the crystal structure is a symmetric binuclear unit made up of two slightly distorted coordination octahedrons, which are bridged by TCB in monodentate fashion to each metal ion. Moreover three nitrogen atoms from three imidazoles, three oxygen atoms from two water molecules and one carboxylate group of TCB coordinated to a nickel (I) ion are found on a face of the octahedron respectively, so the octahedron is a facial isomer.

STRUCTURE OF A POLYMERIC BENZENETETRACARBOXYLATO COMPLEX OF Mn(II) WITH IMIDAZOLE

A novel polymeric μ-BTC complex of Mn(II) with imidazole has been synthesized, where BTC is the 1,2,4,5-benzenetetracarboxylato tetravalent anion, and its crystal structure has been determined by X-ray diffraction methods. The complex crystallizes in the monoclinic spacegroup P21/n with a = 11.184(5), b = 9.177(2), c = 18.243(1)Å and β = 107.84(1)°. Each BTC ligand, located around the crystallographic inversion centre, bridges four Mn(II) atoms through four carboxyl groups to form a three dimensional polymeric structure. The carboxyl groups in the ortho-position of BTC bridges Mn(II) atoms related by the crystallographic screw axis to form helical complex chains along the b axis. Coordination around the Mn(II) atom is distorted octahedral; two BTC anions coordinate to Mn(II), one in unidentate fashion and the other as a chelate. The coordination distance of the unidentate ligand is much shorter than in the chelated ligand.

Voltammetric study of the transfer of Dawson-type heteropolyanions across the nitrobenzene—water interface

A voltammetric study has been made for the transfer of four 18-heteropolymolybdate anions including Dawson anions, i.e. [P 2Mo 18O 62] 6−, [As 2Mo 18O 62] 6−, [S 2Mo 18O 62] 4− and [P 2 Mo 18O 61] 4−, and of a related anion [S 2VMo 17O 62] 5− at the nitrobenzene(NB)—water(W) interface. With regard to the hexavalent and pentavalent anions, well-developed voltammetric waves due to their phase transfer could be obtained under certain conditions. The tetravalent anions, however, gave no wave in the polarizable potential range but showed an increase in the final current rise owing to their transfer from NB to W. From the voltammetric data, the standard ion transfer potential (Δ NB wφ j θ) and standard Gibbs transfer energy (Δ G tr,j θ,NB→W) have been determined (or estimated) for the heteropolyanions. It has been found that Δ NB Wφ j θ and Δ G tr,j θ,NB→W depend primarily on the ionic charge. This is in line with our previous result obtained for Keggin anions in 1991. A possible mechanism has also been proposed for the transfer of the hexavalent Dawson anions.

Relationship between Electron Transport across the Plasmalemma and a pH Decrease in the Bulk Medium

The hypothesis is tested that acidification of the bulk medium during transplasmalemma electron transport to ferricyanide is due solely to a requirement for charge balance. According to this hypothesis, reduction of the trivalent anion, ferricyanide, to the tetravalent anion, ferrocyanide, results in a charge difference that is balanced by protons. A coulometric device is used that rapidly and efficiently reoxidizes ferrocyanide to ferricyanide, thus maintaining a constant charge in the bulk medium. Oat (Avena sativa L. cv Garry) mesophyll protoplasts are chosen as experimental material to facilitate ferricyanide reduction and the concomitant ferrocyanide reoxidation by the coulometric device. The kinetics of ferricyanide reduction and proton excretion by protoplasts are similar to those of other cell types and tissues. Rates of net proton excretion are identical regardless of whether the ferrocyanide is simultaneously reoxidized. We conclude that acidification may occur during transplasmalemma electron transport when there is no change in negative charge of the bulk medium.

Voltammetric study of the transfer of keggin-type heteropolyanions across the nitrobenzene/water interface

The transfer of Keggin-type heteropolyanions, α- and β-[XM 12O 40] 3−/4−, at the nitrobenzene (NB)/water (W) interface has been studied by ion transfer voltammetry (X = Si, Ge, P, As; M = Mo, W). For the tetravalent anions with Si and Ge as the central heteroatoms, well-developed waves due to their phase transfer were observed. On the other hand, the trivalent anions with P and As gave no waves in the polarizable potential range, but showed an increase in the final current rise due to their transfer from NB to W. From the voltammetric data, it has been found that the Gibbs transfer energy, Δ G tr XXX,NB→W, of the heteropolyanions depends primarily on the ionic charge. The extraction behaviour of these heteropoly-acids has been discussed on the basis of the voltammetric data.

Ion fluxes and pH changes induced by trans-plasmalemma electron transfer and fusicoccin in Lemna gibba L. (strain G1)

During the reduction of extracellular [Fe(CN)6](3-) at the plasmalemma of intact, K(+)-starved Lemna gibba L. fronds, the external medium was acidified and K(+) released, in the absence of inhibitors with rates of 10 e(-)/8.5 H(+)/1.5 K(+) (μmol·(g FW)(-1)·(-1)). In K(+) plants the larger K(+) efflux caused a lag phase in extracellular acidification and a change in rates to 10 e(-)/6 H(+)/4 K(+) and in the presence of CN(-)+salicylhydroxamic acid at pH 5 to 5.2 e(-)/0 H(+)/6.6 K(+). The e(-) transfer was accompanied by a membrane depolarization of up to 100 mV and a cytosolic acidification of about 0.6 pH units, but only in K(+) plants, where the extracellular acidification was smaller. These results indicate that a stimulation of the plasmalemma H(+)-ATPase may be triggered either by a cytosolic acidification or by a strong membrane depolarization. It is concluded that the redox system catalyses only uncoupled e(-) transfer without H(+) transfer across the plasmalemma. The obligatory, but secondary charge compensation is partially achieved by the rapid K(+) release upon membrane depolarization and partially by the activity of the plasma membrane H(+)-ATPase, but not by an e(-)/anion exchange. The extracellular acidification during [Fe(CN)6](3-) reduction is generated by the conversion of a strong trivalent into a strong tetravalent anion. This acidification is caused by changes in the concentration ratio of strong cations to strong anions. Efflux of K(+) and not the production of organic acids or NAD(P)H oxidation is the chemical cause of the measurable cytosolic acidification. Extracellular acidification was inversely correlated with intracellular acidification. Similarly, fusicoccin-induced pH changes were correlated with changes in the strong-ion concentration difference. Extracellular ± FC-dependent acidification and intracellular alkalinization of up to 0.6 pH units were strongly dependent on K(+) fluxes. The ferricyanide-triggered trans-plasmalemma electron-transfer system is an example of how measurable pH changes are the consequence and not the cause of charge-transfer-induced changes in strong-ion fluxes.

Why is Mg 2+ necessary for specific cleavage of the terminal phosphoryl group of ATP?

The mechanism of specific cleavage of the terminal phosphoryl group in hydrolysis of ATP, and the role of Mg 2+ in the hydrolysis were studied by ab initio molecular orbital calculations. The tetravalent anion of methyl triphosphate was used as a model of the ATP anion, and its electronic structures were determined as a function of the distance between Mg 2+ and its β-phosphoryl group. We found that the closer location of Mg 2+ to the β-phosphoryl group than to the α- or γ-phosphoryl group was effective in weakening the P-O bond at which the cleavage of ATP catalysed by most enzymes takes place. Moreover, the orbital coefficient of the frontier electron of Pγ, which is related to the nucleophilic reaction, was shown to increase greatly with increasing interaction between Mg 2+ and the β-phosphoryl group.

Role of partially flocculated sols in emulsion stability

The stability of emulsion of Toluene in water stabilized by partially flocculated ferric hydroxide sol has been studied. The size of the emulsion droplets as determined by size frequency analysis is found to be of 1.1 μ radius. The flocculation studies were carried out haemocytometrically at different amount of electrolytes and at different pH values. The electrokinetic potential ‘ζ’ was determined micro-electrophoretically at different amounts of electrolytes and also at different pH's. In the case of tri and tetra valent anions the charge reversal was observed. In the light of the D.V.O. theory the interaction energy profiles were drawn and 2–6 kT deep secondary minima obtained showing thereby the occurrence of reversible flocculation. Degree of aggregation has been calculated theoretically at different values of ‘A’ and the value of A was found to be 1.0×10−12 erg to fit the value of degree of aggregation obtained haemocytometrically. The charge densities and binding parameters have also been calculated.

THE MECHANISM BY WHICH TRIVALENT AND TETRAVALENT IONS PRODUCE AN ELECTRICAL CHARGE ON ISOELECTRIC PROTEIN

1. Experiments on anomalous osmosis suggested that salts with trivalent cations, e.g. LaCl(3), caused isoelectric gelatin to be positively charged, and salts with tetravalent anions, e.g. Na(4)Fe(CN)(6), caused isoelectric gelatin to be negatively charged. In this paper direct measurements of the P.D. between gels of isoelectric gelatin and an aqueous solution as well as between solutions of isoelectric gelatin in a collodion bag and an aqueous solution are published which show that this suggestion was correct. 2. Experiments on anomalous osmosis suggested that salts like MgCl(2), CaCl(2), NaCl, LiCl, or Na(2)SO(4) produce no charge on isoelectric gelatin and it is shown in this paper that direct measurements of the P.D. support this suggestion. 3. The question arose as to the nature of the mechanism by which trivalent and tetravalent ions cause the charge of isoelectric proteins. It is shown that salts with such ions act on isoelectric gelatin in a way similar to that in which acids or alkalies act, inasmuch as in low concentrations the positive charge of isoelectric gelatin increases with the concentration of the LaCl(3) solution until a maximum is reached at a concentration of LaCl(3) of about M/8,000; from then on a further increase in the concentration of LaCl(3) diminishes the charge again. It is shown that the same is true for the action of Na(4)Fe(CN)(6). From this it is inferred that the charge of the isoelectric gelatin under the influence of LaCl(3) and Na(4)Fe(CN)(6) at the isoelectric point is due to an ionization of the isoelectric protein by the trivalent or tetravalent ions. 4. This ionization might be due to a change of the pH of the solution, but experiments are reported which show that in addition to this influence on pH, LaCl(3) causes an ionization of the protein in some other way, possibly by the formation of a complex cation, gelatin-La. Na(4)Fe(CN)(6) might probably cause the formation of a complex anion of the type gelatin-Fe(CN)(6). Isoelectric gelatin seems not to form such compounds with Ca, Na, Cl, or SO(4). 5. Solutions of LaCl(3) and Na(4)Fe(CN)(6) influence the osmotic pressure of solutions of isoelectric gelatin in a similar way as they influence the P.D., inasmuch as in lower concentrations they raise the osmotic pressure of the gelatin solution until a maximum is reached at a concentration of about M/2,048 LaCl(3) and M/4,096 Na(4)Fe(CN)(6). A further increase of the concentration of the salt depresses the osmotic pressure again. NaCl, LiCl, MgCl(2), CaCl(2), and Na(2)SO(4) do not act in this way. 6. Solutions of LaCl(3) have only a depressing effect on the P.D. and osmotic pressure of gelatin chloride solutions of pH 3.0 and this depressing effect is quantitatively identical with that of solutions of CaCl(2) and NaCl of the same concentration of Cl.

ELECTRICAL CHARGES OF COLLOIDAL PARTICLES AND ANOMALOUS OSMOSIS

1. It has been shown in previous publications that when solutions of different concentrations of salts are separated by collodion-gelatin membranes from water, electrical forces participate in addition to osmotic forces in the transport of water from the side of the water to that of the solution. When the hydrogen ion concentration of the salt solution and of the water on the other side of the membrane is the same and if both are on the acid side of the isoelectric point of gelatin (e.g. pH 3.0), the electrical transport of water increases with the valency of the cation and inversely with the valency of the anion of the salt in solution. Moreover, the electrical transport of water increases at first with increasing concentration of the solution until a maximum is reached at a concentration of about M/32, when upon further increase of the concentration of the salt solution the transport diminishes until a concentration of about M/4 is reached, when a second rise begins, which is exclusively or preeminently the expression of osmotic forces and therefore needs no further discussion. 2. It is shown that the increase in the height of the transport curves with increase in the valency of the cation and inversely with the increase in the valency of the anion is due to the influence of the salt on the P.D. (E) across the membrane, the positive charge of the solution increasing in the same way with the valency of the ions mentioned. This effect on the P.D. increases with increasing concentration of the solution and is partly, if not essentially, the result of diffusion potentials. 3. The drop in the transport curves is, however, due to the influence of the salts on the P.D. (epsilon) between the liquid inside the pores of the gelatin membrane and the gelatin walls of the pores. According to the Donnan equilibrium the liquid inside the pores must be negatively charged at pH 3.0 and this charge is diminished the higher the concentration of the salt. Since the electrical transport is in proportion to the product of E x epsilon and since the augmenting action of the salt on E begins at lower concentrations than the depressing action on epsilon, it follows that the electrical transport of water must at first rise with increasing concentration of the salt and then drop. 4. If the Donnan equilibrium is the sole cause for the P.D. (epsilon) between solid gelatin and watery solution the transport of water through collodion-gelatin membranes from water to salt solution should be determined purely by osmotic forces when water, gelatin, and salt solution have the hydrogen ion concentration of the isoelectric point of gelatin (pH = 4.7). It is shown that this is practically the case when solutions of LiCl, NaCl, KCl, MgCl(2), CaCl(2), BaCl(2), Na(2)SO(4), MgSO(4) are separated by collodion-gelatin membranes from water; that, however, when the salt has a trivalent (or tetravalent?) cation or a tetravalent anion a P.D. between solid isoelectric gelatin and water is produced in which the wall assumes the sign of charge of the polyvalent ion. 5. It is suggested that the salts with trivalent cation, e.g. Ce(NO(3))(3), form loose compounds with isoelectric gelatin which dissociate electrolytically into positively charged complex gelatin-Ce ions and negatively charged NO(3) ions, and that the salts of Na(4)Fe(CN)(6) form loose compounds with isoelectric gelatin which dissociate electrolytically into negatively charged complex gelatin-Fe(CN)(6) ions and positively charged Na ions. The Donnan equilibrium resulting from this ionization would in that case be the cause of the charge of the membrane.