Acid Rinse Research Articles

Photosynthesis of Cladophora in Relation to Light and CO2 Limitation CaCO3 Precipitation

In productivity studies of Cladophora by the light—and—dark—bottle method, errors may arise from CaCo3 precipitation, self—shading, pH/Co2 limitation, or variations in the condidtion of the alga. Precipitation of CaCo3 and MgCo3 by Cladophora may equal one—third of production at pH 9.3 to 10.4, resulting in overestimation of photosynthesis by either the 14C or pH method. The calcification is readily removed by acid rinse without loss of fixed carbon. Consideration of such errors in relation to a recent study leads to the refutation of the conclusion the Cladophora shows an unusual ability to utilize low light intensities.

Creasable Dimethyloldihydroxyethyleneurea-Crosslinked Cotton Print Cloth

Creasable wrinkle-resistant cotton print cloths were prepared by crosslinking with dimethyloldihydroxyethyleneurea (DMDHEU) in the presence of phosphorylating agents as catalysts and reactants. These fabrics were wrinkle resistant and, because of the catalytic action of the acidic phosphoryl groups present, could be given creases which were durable to laundering. The treatments were applied by a conventional laboratory pad-dry-cure technique. Fabric treated with the DMDHEU-sodium dihydrogen phosphate combination had a conditioned warp wrinkle recovery angle of 134° and retained 60% of its warp' breaking strength. Creases, which were excellent after five launderings, could be developed in this fabric after a mildly acidic rinse and ironing or pressing. A fabric treated with the DMDHEU-sodium hexametaphosphate combination had a warp conditioned wrinkle recovery angle of 136° and retained 55% of its breaking strength. Creases developed in this fabric also were excellent after laundering. Effects of process variables, such as concentration of phosphorylating agent, curing time and temperature, and added softener, are described, and creasing conditions and variables are discussed.

Monitoring Sodium Contamination in Silicon Devices and Processing Materials by Flame Emission Spectrometry

Sources of sodium contamination found in routine chemical treatment and handling of silicon slices have been identified and quantitatively measured using a flame photometric technique. Common processing chemicals generally contain less than 500 ppb of sodium. Ways to reduce the level of sodium contamination during silicon device processing have been determined. Sodium may generally be rinsed off silicon and silicon‐dioxide‐covered silicon slices with a dilute acid rinse followed by a deionized water rinse. Subsequent handling and contact with the slices should be done with freshly cleaned handling tools to prevent recontamination.

A study of the biochemistry and cytochemical localization of -glycerophosphatase activity in root tips of maize and pea.

A critical study has been made of the standard lead phosphate precipitation technique for the localization ofβ-glycerophosphatase activity in young root tips. The effects of fixatives on enzyme activity and on the loss of activity during fixation and incubation have been determined. Cytochemical studies showed that the most prominent sites ofβ-glycerophosphatase activity were at particulate sites in the cytoplasm and in the nucleus. Good correlation was obtained between frozen section and electron microscope studies although a number of problems were encountered. These particularly concerned the penetration of the staining medium, the loss of activity during incubation and the use of the acetic acid rinse. Recommendations are made for the reliable localization of the enzyme. The use of controls in this method were studied and their validity discussed.

Comparative analysis of cleaning ability of three nickel-titanium rotary systems: ProTaper universal, K3 and Mtwo: An in vitro scanning electron microscopic study.

Endodontic instruments including the nickel-titanium (NiTi) instruments produce debris and smear layer during instrumentation. The study was carried out to evaluate and compare the cleaning effectiveness of root canal preparation using three different rotary NiTi instrumentation systems - ProTaper Universal, K3 and Mtwo by means of scanning electron microscopy (SEM). Thirty-six freshly extracted permanent mandibular molars were randomly divided into four groups: ProTaper Universal, K3, Mtwo system and control group. The mesiobuccal canal was cleaned and shaped with rotary instruments. The intracanal irrigant used after each instrument was 3 mL of 3% sodium hypochlorite (NaOCl). After the cleaning and shaping was completed, a 1-min 17% ethylenediaminetetraacetic acid rinse was followed by a final NaOCl rinse. All samples were decoronated. Mesial roots were sectioned buccolingually and examined under SEM at 500× magnification in three areas of root canal. Canal walls were quantitatively evaluated using a five-score evaluation scale. Statistical analysis was done using Kruskal-Wallis test, Fisher's exact test and weighted kappa. Completely clean canals were not found in any of the groups. The mean value of debris score for ProTaper, K3 and Mtwo was 2.35, 2.41 and 2.22 respectively. There was no statistically significant difference between the three tested groups (P = 0.237). The apical thirds of the canal was found to be significantly less clean than coronal and middle thirds irrespective of the system used. There was no statistically significant difference between the three tested groups - ProTaper, K3 and Mtwo in cleaning different regions of the canal - coronal, middle and apical.

Exchange and Absorption of Cations by Excised Roots

AbstractBarley (Hordeum Vulgare) corn (zea Mays L.), and soybeans (Glycline max) were given pretreatments which were designed to alter the root cation‐exchange capacity. The amounts of Ca and K absorbed by the excised roots after a 1 hour uptake period in 10‐3N chloride solution were displaced by a series of successive rinses ranging in pH from 2 to 12. There was a significant linear correlation between uptake of both Ca and K and the exchangeable Ca and K in several of the rinses, particularly with the exchangeable ions which were not removed by the first acid rinse but which were removed with subsequent rinses. Multiple correlation coefficients for these relationships ranged from 0.79 to 0.96. The method of fractionating the adsorbed ions showed promise for studying exchange properties of plant roots.

Optical Measurement of Film Growth on Silicon and Germanium Surfaces in Room Air

The thickness and growth kinetics of oxide films on polished silicon and germanium exposed to room air after having been rinsed in hydrofluoric acid were obtained by measuring the ellipticity of reflected polarized light. Film growth obeys the Elovich equation. Plots of thickness vs. the logarithm of the time in air are linear after about 15000 sec with slopes of 6.8Aå/decade (Si) and 8.1Aå/decade (Ge). Immediately after the hydrofluoric acid rinses the films are 10–15Aå thick and increase in thickness by about 11–12Aå after one day in air. A small part of the films dissolves in certain organic liquids. Measurements of ellipticity at two angles of incidence during film growth gave an experimental check of the optical theory.

A Nile blue staining technic for the differentiation of melanin and lipofuscins.

When paraffin sections are stained in 0.05-.01% Nile blue in 1 % sulfuric acid, washed thoroughly in water and mounted in aqueous media, lipofuscins color deep blue, melanins dark green, myelin and red cells lighter greens and background pale green. If, immediately after staining, the preparations are at once extracted with acetone with or without a 1% sulfuric acid rinse, melanins remain dark green, mast cells color purple, lipofuscins and background decolorize and nuclei may stain light green.

Calcium Scums and Sludges in Photography<!--<xref ref-type="other" rid="fn1-10.5594_J07990">*</xref>-->

Calcium salts may be introduced into photographic processing solutions from (a) the water supply, (b) the emulsion, or both, and these salts combine with some of the developer constituents to form insoluble compounds which may appear as (1) a sludge suspended in the developer or accumulated on the filters, (2) a scum on the film, or (3) a scale on rollers, sprockets, racks, and the walls of tanks. The control of the water supply will reduce the quantity of these precipitates and the scum may be removed by suitable acid rinse or acid fixing baths, but calcium-sequestering agents are often used for more complete control. When selecting these agents, their calcium-sequestering power, stability, photographic effect, and their effect when carried over into the fixing bath must be considered, and on the basis of these requirements, sodium tetraphosphate was found the most suitable.† — Appropriate quantities of sodium tetraphosphate added to the developer were found to (1) prevent sludge formation in mixing, storing, or use of the developer, (2) prevent the formation of scum on the film when in the developer, and (3) greatly diminish the rate at which incrustations accumulate on the tank walls, sprockets, and mechanical parts. — If developers are stored at high temperatures, the polyphosphates present tend to hydrolyze to the simple phosphates which, when carried over into the fixing bath, may precipitate as aluminum phosphate. This hydrolysis does not occur on storage of the dry solids and only very slowly below 85 F when in solution. Solutions stored at high temperatures or for prolonged periods may be protected by the addition of sodium citrate which extends the life of the tetraphosphate solution and prevents precipitation in the fixing bath if hydrolysis has occurred.