Ammonium Magnesium Phosphate Research Articles

Incidence of bubbles on samples cast in a phosphate-bonded investment

P hosphate-bonded investments are widely used to produce castings of high-fusing alloys for both ceramometal and all-metal dental restorations. These investments are generally stronger, more refractory, and can be manipulated for a greater degree of mold expansion than gypsum-bonded investments. The investments are primarily composed of 75% to 90% silica refractory in the form of quartz or cristobalite, which is initially bound together by magnesium and ammonium magnesium phosphate formed by reaction of magnesium oxide with monoammonium phosphate in water. High temperature burnout results in loss of water, crystallization, recrystallization of magnesium phosphates and formation of silicophosphate glasses, which give the mold high strength at casting temperatures.“’ An unfortunate sideeffect of the initial setting reaction is the liberation of gas (presumably ammonia) bubbles, which often adhere to the surface of the wax pattern and result in positively cast nodules on the surface of the casting (Fig. 1). Such nodules interfere with the fit of the casting and must be removed before the casting is clinically serviceable. This is time-consuming and troublesome for the dental technician and may compromise the fit of the casting if excessive internal grinding is required. It was the purpose of this study to examine the effect of a number of investing variables on the incidence of bubbles cast to wax patterns invested in a phosphatebonded investment. The following investing variables were examined. 1. Liquid/powder ratios 2. Mixing time under vacuum 3. Low speed (hand) vs. high speed (machine) mixing 4. Special liquid/water ratios for a fixed total L/P ratio 5. Use of a debubblizer

Effects of phosphate, glucose, and ammonium on cell growth and lincomycin production by Streptomyces lincolnensis in chemically defined media

Cell growth and lincomycin production were measured in batch cultures of Streptomyces lincolnensis in chemically defined media. In these fermentations the specific rate of antibiotic production was maximal during growth and always declined at the end of the growth phase. It was found that both phosphate and ammonium salts, while required for cell growth, had negative effects on antibiotic production. By increasing the concentration of magnesium sulfate, it was possible to increase both the production rates and final titers of lincomycin. The mechanism for this effect was found to be the reduction of soluble phosphate in the medium through the precipitation of ammonium magnesium phosphate. Lincomycin production rates were not inhibited by glucose at concentrations of up to 30 g/L.

X-ray microanalysis of spontaneously formed urinary calculi in a jaundiced strain of rat

A high incidence of spontaneously formed urinary stone was found in the females of a jaundiced strain of rat developed from a cross between Gunn's rat and Wistar-Imamichi rat. In this colony, 42.3% of the females had urinary calculi. Elemental analyses of these urinary calculi were carried out with an analytical electron microscope, a high-resolution transmission electron microscope fitted with an energy dispersive type X-ray microanalyzer and a scanning device. In the surface and middle areas of the stone, the main components were recognized as magnesium (Mg) and phosphorus (P). In the central region of the stone, calcium (Ca) and phosphorus (P) were found as the main elements with trace amounts of sodium (Na), chlorine (Cl), and potassium (K). The analyses indicated that the spontaneous urinary stone consisted of phosphate salts with calcium or magnesium. In addition, the mass ratio of the Mg P or Ca P in the stones was calculated from X-ray pulse intensity ratios and compared with the mass ratio of a standard sample. The results suggested that the magnesium and phosphorus in the urinary stones existed as ammonium magnesium phosphate, MgNH 4PO 4, and the calcium and phosphorus as tribasic calcium phosphate, Ca 3(PO 4) 2.

Enteroliths in Horses—a retrospective study of 30 cases

In a retrospective study of selected cases, abdominal colic in 30 horses was attributed to enterolith obstructions of the large intestine. Obstructions caused by "true" enteroliths were confined to horses more than four years old. Prominent clinical features were recurrent mild abdominal pain, inappetance, gaseous distension and minimal intestinal motility. The various aspects of the clinical syndrome, including diagnostic problems and clinical management, are discussed. Most obstructing enteroliths were found near the beginning of the small colon and most horses contained only a single major concretion. Enteroliths were formed by mineral deposition in concentric layers about a central nidus of ingested material and were spherical or tetrahedral in shape. Intestinal concretions were found to consist primarily of ammonium magnesium phosphate.

Urolithiasis in the rat

As incidental findings uroliths were observed in the renal pelvis of Sprague-Dawley rats in an 18-month toxicity study. Of 220 rats examined, uroliths were found in 55 (35 males and 20 females). Infrared spectral analysis of the stones indicated a content of ammonium magnesium phosphate. Formation of the uroliths may have started by mineralization of degenerating hyperplastic epithelium of the renal papilla.

Combined Radiochemical-Neutron Activation Analysis Method for the Determination of Sulfur and Phosphorus in High Purity Paper and Beer.

Sulfur and phosphorus were evaluated by a mathematical treatment of the specific activities, expressed as /sup 32/P, of analyzed materials and of standards after a double irradiation with and without cadmium protection of the targets. After demineralization of the sample by treatment with acid and evaporation of the whole solution to dryness, phosphorus was extracted with ether containing 5% sulfuric acid, and then precipitated as ammonium magnesium phosphate followed by a beta count of /sup 32/P. Numerical data were obtained for American and Greek papers and for beers of different types and origin. The sensitivity of this method reaches the value of 10/sup -3/ ppm for sulfur and phosphorus determinations. (auth)

Formation of ammonium magnesium phosphate crystals in cultures of fungi growing on keratin.

Formation of ammonium magnesium phosphate crystals in cultures of fungi growing on keratin.

Exploratory investigations on the chemistry and technology of fertilizers and salts

From this review of exploratory work we can 1) decide to some extent which results of the exploratory work deserve further development and utilization, and 2) arrive at some general views concerning the development of the exploratory investigations. 1. Subjects that require further development and later, possibly, exploitation under manufacturing conditions include: thermal dissociation of calcium phosphates with formation of P2O5; defluorination of phosphates in a fluid bed with natural gas; the process of fusing Kara-Tau phosphorites without use of steam; the preparation of ammonium and potassium metaphosphates of various solubilities; the preparation of ammonium magnesium phosphate monohydrate; the absorption of hydrogen fluoride by solid absorbents such as limestone and nepheline. The theoretical investigations that must be more extensively and thoroughly developed include: a) study of the relation between the agronomic effectiveness of various phosphate compounds and their compositions and structures (with the use of radioactive P and Ca isotopes); b) investigation of the physicochemical conditions for the polymerization of P2O5 and metaphosphates and development of methods for determining the degree of polymerization. 2. The development of exploratory investigations is an important and absorbing task. The important task of the supervisors and teachers is to instill the taste for pioneering, creative, exploratory work.

The Specific Gravity of Rubber in Hevea Latex

Abstract Since my former communication on this subject several papers have appeared which form valuable contributions to the interesting problem of the actual specific gravity of the rubber particles in (original or preserved) Hevea latex. Rhodes recalculated his data, and came to an average figure of 0.9064 for the specific gravity of rubber in ammoniated latex, preserved during several weeks in the East; the rubber content being determined after coagulation by acetic acid in the usual way. Using the term proposed in my former paper, this may be called the specific gravity of “crepe rubber in preserved latex”, which may differ from that of “crepe rubber in original latex” by the effect of possible changes by the prolonged action of ammonia, by the settling out of the sludge (ammonium magnesium phosphate, mixed with protein-like substances), and other changes that occur in preserved latex. Leaving these unknown factors out of consideration, we have to take into account the fact that the rubber content was determined by acid coagulation, which means that a certain amount of serum substances, principally proteins, was precipitated with the rubber, and may have influenced its specific gravity. In my former communication I have shown that the specific gravity of “crepe rubber in latex” is found lower, the higher the rubber content of the original latex, i.e., the smaller the ratio of serum to rubber, and the smaller, therefore, the amount of acid-precipitated serum proteins in per cent of the rubber. Plotting, in this line of thought, Rhodes' figure in the graph (Figure 1), it will be seen that it corresponds to 45 grams rubber per 100 cc, or about 46.6 in percentage of weight, not abnormal for a preserved latex. Protein, precipitated with the rubber, has a still smaller effect in another figure given by Rhodes, namely, the specific gravity of rubber from a centrifuged cream of 56.7 per cent rubber content (acid coagulation). The corrected figure for the specific gravity of this rubber is given by Rhodes as 0.9011, which in Figure 1 corresponds to 55.5 grams of rubber per 100 cc, or about 58.5 per cent by weight; this is in reasonable agreement with the real figure of 56.7, taking into account the unavoidable errors of an extrapolation, such as in Figure 1.

Availability studies on magnesium in magnesic limestones, serpentine, olivine, and magnesium ammonium phosphate

The availability of magnesium in different magnesic limestones, Serpentine, Olivine and ammonium magnesium phosphate was studied in pot cultures using Irish Cobbler potatoes grown in a magnesiumdeficient soil as the plant indicator. In a similar manner the effect on tuber yields of the addition of calcium carbonate, magnesium sulfate, and extra potash to this soil has been determined. The results may be summarized as follows:

Societies and Academies

Societies and Academies

210. Studies of phosphates. Part I. Ammonium magnesium phosphate and related compounds

210. Studies of phosphates. Part I. Ammonium magnesium phosphate and related compounds

The constitution of the ammonium-magnesium phosphate of analysis

The constitution of the ammonium-magnesium phosphate of analysis