Quantitative chemical analysis on paper: Determination of phosphate in the presence of large quantities of other ions

Summary A rapid method has been developed for the determination of phosphate by means of filter paper impregnated with lead iodide. A sample is added to the impregnated filter paper by means of a capillary, and after irrigation to cause migration of the ions a white spot is obtained as the lead iodide is converted into the phosphate. The weight of the spot is dependent on the p_H and the quantity of phosphate present.The determination is possible in the presence of SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, succinic, citric and tartaric acids. The determination is impossible in the presence of C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2–, or CO₃ ^2–.The method permits the determination of 7–100g of phosphate with an accuracy of 2%.

---

Zusammenfassung Ein schnelles Verfahren zur Phosphatbestimmung wird besehrieben, bei dem man sich eines mit Bleijodid imprägnierten Filterpapiers bedient. Die Probe wird mit einer Kapillare auf das Papier aufgebracht. Man erleichtert die Ionenbewegung durch geeignete Befeuchtung und erhält einen weißen Fleck infolge Umsetzung des Bleijodids in -phosphat. Das Gewicht des Fleckens hängt vom p_H und von der Phosphatmenge ab.Die Bestimmung ist möglich in Gegenwart von SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, J^–, JO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, Bernsteinsäure, Zitronensäure und Weinsäure; sie ist nicht möglich bei Gegenwart von C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– oder CO₃ ^2–. 7 bis 100g Phosphat können mit einer Genauigkeit von 2% bestimmt werden.

---

Résumé On a développé une méthode rapide pour le dosage des phosphates sur papier-filtre imprégné d'iodure de plomb. On dépose l'échantillon sur le papier-filtre imprégné, à l'aide d'un capillaire, et, après humidification pour provoquer la migration des ions, on obtient une tache blanche quand l'iodure de plomb est converti en phosphate. Le poids de la tache dépend du p_H et de la quantité de phosphate présent.Le dosage est possible en présence de SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, et des acides succinique, citrique et tartrique. Il est impossible en présence de C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– ou CO₃ ^2–.La méthode permet le dosage de 7 à 100g de phosphate avec une précision de 2%.

     

Microdetermination of Copper(II) by an exchange reaction on paper

Summary Two methods are given for the determination of copper in very dilute solutions in water (1g/ml). The sample is passed through filter paper impregnated with cadmium sulphide. Copper, lead, mercury, silver and bismuth ions at p^H1.5–2 give an exchange reaction with the cadmium and are caught on the paper. When the paper is washed free from acid, dried, and treated with potassium cyanide, only the copper sulphide reacts. The excess of cyanide can be determined by its reaction with a filter impregnated with silver chloride, the size of the spot washed free from silver being a measure of the amount of cyanide. No other ions interfere with this method. If the other exchanging ions are absent, the copper can be estimated directly from the intensity of the copper sulphide stain on the cadmium sulphide paper, a standard series of stains being used for comparison. The range is 10–150g of copper in 500–1000 ml the error being 3% for the cyanide method, and 7–8% for the standard series method.

---

Zusammenfassung Zwei Bestimmungsmethoden für Cu in sehr verdünnten wäßrigen Lösungen (1g/ml) werden angegeben. Man läßt die Probe durch ein mit CdS imprägniertes Filterpapier laufen. Cu, Pb, Hg, Ag und Bi werden bei p^H 1,5 bis 2 durch eine Austauschreaktion auf dem Papier festgehalten. Wird dieses säurefrei gewaschen, getrocknet und mit KCN behandelt, so reagiert nur CuS. Der Cyanidüberschuß kann durch seine Reaktion mit einem AgCl-imprägnierten Filter bestimmt werden, wobei das freigewaschene Silber als Maß für die Cyanidmenge dient. Die Methode wird von keinen anderen Ionen gestört. Fehlen die vier neben Cu genannten Ionen, so läßt sich die Cu-Menge direkt aus der am CdS-Papier entstehenden Färbung schätzen, wozu man. sich einer Reihe von Standardfärbungen bedient. 10 bis 150g Cu lassen sich in 500 bis 1000 ml mit einem Fehler von 3% nach der Cyanidmethode, und 7 bis 8% mit Hilfe der Standardreihe bestimmen.

     

Controlled Annealing in Adaptive Multicomponent Gels

We use a pH-driven annealing process to convert between co-assembled and self-sorted networks in multicomponent gels. The initially formed gels at low pH are co-assembled, with the two components coexisting within the same self-assembled structures. We use an enzymatic approach to increase the pH, resulting in a gel-to-sol transition, followed by a hydrolysis to lower the pH once again. As the pH decreases, a self-sorted network is formed by a two-stage gelation process determined by the pK_a of each component. This approach can be expanded to layered systems to generate many varied systems by changing composition and rates of pH change, adapting their microstructure and so allowing access to a far greater range of morphologies and complexity than can be achieved in single component systems.     

Implicit standard Jacobi gives high relative accuracy

We prove that the Jacobi algorithm applied implicitly on a decomposition A = XDX ^T of the symmetric matrix A, where D is diagonal, and X is well conditioned, computes all eigenvalues of A to high relative accuracy. The relative error in every eigenvalue is bounded by O(ek(X)){O(\epsilon \kappa (X))} , where e{\epsilon} is the machine precision and k(X) o ||X||₂·||X^-1||₂{\kappa(X)\equiv\|X\|_2\cdot\|X^{-1}\|_2} is the spectral condition number of X. The eigenvectors are also computed accurately in the appropriate sense. We believe that this is the first algorithm to compute accurate eigenvalues of symmetric (indefinite) matrices that respects and preserves the symmetry of the problem and uses only orthogonal transformations.     

Accurate and efficient evaluation of Schur and Jack functions

We present new algorithms for computing the values of the Schur and Jack functions in floating point arithmetic. These algorithms deliver guaranteed high relative accuracy for positive data ( 0$">) and run in time that is only linear in .

     

EPR and electronic spectral properties of aryl-substituted bis(dithiophosphato)copper(II) complexes

The spectral properties of bis(diaryl-dithiophosphato)copper(II) complexes, [Cu(S(2)P(OR)(2))(2)], with R = o-cresyl (complex I) and 2,6-dimethylphenyl (complex II) are studied by EPR- and vis spectroscopy. In solid (powder) state both complexes exhibit dark brown colour and are paramagnetic. Room temperature EPR spectra of the complexes dissolved in non-coordinating (C(6)H(5)CH(3), C(5)H(12), C(6)H(14)), acceptor (CHCl(3), CCl(4)) or donor (DMFA, DMSO) solvents have typical features of the chromophore CuS(4). In non-coordinating and acceptor solvents their isotropic EPR parameters are: g(iso)=2.047+/-0.003, (Cu)A(iso) = 7.2+/-0.1 mT and (P)A = 0.95+/-0.1 mT. An absorption band characterizes the vis spectra in these solvents with a maximum at 427 nm, due to a ligand-to-metal charge-transfer transition. One hour after dissolution the absorbance at 427 nm follows Beer's law with molar absorptivity (epsilon) about 11000, which does not change significantly after 24 h staying at room temperature or after 30 min heating at 50 degrees C. Both DMFA and DMSO exhibit specific solute-solvent interaction with the acceptor centre of copper complex yielding an axial adduct, with increased g-factor and decreased (hf)A compared to the initial complex. An additional EPR signal with unresolved hyperfine structure is also detected in DMSO. EPR and vis intensities of both bis(diaryl-dtp)Cu(II) complexes decrease after dissolution in both solvents. Moreover, they are EPR silent in pyridine and do not show any absorption in the vis spectra.     

Mechano-transduction of DNA hybridization and dopamine oxidation through electrodeposited chitosan network

While microcantilevers offer exciting opportunities for mechano-detection, they often suffer from limitations in either sensitivity or selectivity. To address these limitations, we electrodeposited a chitosan film onto a cantilever surface and mechano-transduced detection events through the chitosan network. Our first demonstration was the detection of nucleic acid hybridization. In this instance, we electrodeposited the chitosan film onto the cantilever, biofunctionalized the film with oligonucleotide probe, and detected target DNA hybridization by cantilever bending in solution (static mode) or resonant frequency shifts in air (dynamic mode). In both detection modes, we observed a two-order of magnitude increase in sensitivity compared to values reported in literature for DNA immobilized on self-assembled monolayers. In our second demonstration, we coupled electrochemical and mechanical modes to selectively detect the neurotransmitter dopamine. A chitosan-coated cantilever was biased to electrochemically oxidize dopamine solution. Dopamine's oxidation products react with the chitosan film and create a tensile stress of approximately 1.7 MPa, causing substantial cantilever bending. A control experiment was performed with ascorbic acid solution. It was shown that the electrochemical oxidation of ascorbic acid does not lead to reactions with chitosan and does not change cantilever bending. These results suggest that chitosan can confer increased sensitivity and selectivity to microcantilever sensors.     

Quantitative chemical analysis on paper: Micro-determination of copper and a mixture of copper and silver

Summary A method has been suggested for the determination of small amounts of copper and of mixtures of copper and silver using filter paper impregnated with silver chloride and sodium carbonate. The method depends on competition between copper and silver ions to form complexes with cyanide added to the paper. The area of the spot produced by conversion of AgCl into Ag(CN)₂ ^– is measured by weight, and is inversely proportional to the amount of copper present, since the Cu(CN)₄ ^3– complex is preferentially formed. The silver present is determined separately, and the amount of copper calculated.The determination is possible in the presence of Bi³⁺, C³⁺, Mn²⁺, Pb²⁺, K⁺, Na⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, NH₄ ⁺, Al³⁺, Sn²⁺, Hg²⁺, Ag⁺, Fe²⁺, Fe³⁺, NO₃ ^–, SO₄ ^2–, CO₃ ^2–, CrO₄ ^2–, Cl^–, Br^–, and SCN^–.The determination is impossible in the presence of I^–, I₂, Zn²⁺, Cd²⁺, Hg₂ ²⁺, Co²⁺, or Ni²⁺.The method permits the determination of 4–30g of copper and 8–60g of silver with an accuracy of 2%.

---

Zusammenfassung Eine Methode zur Bestimmung kleiner Kupfermengen und von Kupfer-Silber-Gemischen mit Hilfe von Filtrierpapier wird vorgeschlagen, das mit Silberchlorid und Natriumcarbonat imprägniert ist. Sie beruht auf der Konkurrenz zwischen Kupfer und Silber bei der Komplexbildung mit Cyanid, das man auf das Papier aufbringt. Das Flächenausmaß des durch Komplexierung des Silbers gebildeten Fleckens wird gravimetrisch bestimmt. Es ist umgekehrt proportional zur Menge anwesenden Kupfers, da [Cu(CN)₄]^3– bevorzugt gebildet wird. Das Silber wird getrennt bestimmt und so die Kupfermenge berechnet.Die Bestimmung ist möglich in Gegenwart von Bi³⁺, Cr³⁺, Mn²⁺, Pb²⁺, K⁺, Na⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, NH₄ ⁺, A1³⁺, Sn²⁺, Hg²⁺, Ag⁺, Fe²⁺, Fe³⁺, NO₃ ^–, SO₄ ^2–, CO₃ ^2–, CrO₄ ^2–, Cl^–, Br^– und SCN^– und nicht möglich in Gegenwart von J^–, J₂, Zn²⁺, Cd²⁺, Hg₂ ²⁺, Co²⁺ oder Ni²⁺.4 bis 30g Kupfer sowie 8 bis 60g Silber können mit einer Genauigkeit von 2% bestimmt werden.

---

Résumé On propose une méthode pour doser de petites quantités de cuivre et de mélanges de cuivre et d'argent, à l'aide de papier-filtre imprégné de chlorure d'argent et de carbonate de sodium. La méthode dépend de l'effet compétitif entre les ions cuivre et argent pour former les complexes avec le cyanure déposé sur le papier. La surface de la tache formée en transformant le chlorure d'argent en Ag(CN)₂ ^– est mesurée par pesée et est inversement proportionnelle à la quantité de cuivre présent, puisque le complexe Cu(CN)₄ ^3– se forme préférentiellement. L'argent présent est dosé séparément et la quantité de cuivre s'en déduit par calcul.Le dosage est possible en présence de Bi³⁺, Cr³⁺, Mn²⁺, Pb²⁺, K⁺, Na⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, NH₄ ⁺, Al³⁺, Sc³⁺, Hg²⁺, Ag⁺, Fe²⁺, Fe³⁺, NO₃ ^–, SO₄ ^2–, CO₃ ^2–, CrO₄ ^2–, Cl^–, Br^– et SCN^–.Le dosage est impossible en présence de I^–, I₂ ^–, Zn²⁺, Cd²⁺, Hg²⁺, Co²⁺ ou Ni²⁺. La méthode permet le dosage de 4 à 30g de cuivre et de 8 à 60g d'argent avec une précision de 2%.