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  • 1
    Electronic Resource
    Electronic Resource
    A double-blind comparison of felodipine and hydrochlorothiazide added to metoprolol to control hypertension (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 21-24 
    Details
    ISSN: 1432-1041
    Keywords: felodipine ; metoprolol ; hydrochlorothiazide ; hypertension ; blood pressure ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Seventy-six uncomplicated hypertensive patients treated in General Practice, whose seated diastolic blood pressure (Phase V) (dBP) remained ≥95 mmHg after a minimum of 4 weeks treatment with metoprolol 50 mg b.i.d. as antihypertensive monotherapy, were randomized to receive the selective ‘calcium antagonist’ felodipine 5 mg b.i.d. or hydrochlorothiazide 12.5 mg b.i.d. in addition to metroprolol 50 mg b.i.d. The trial duration was 8 weeks, the dose of the felodipine or hydrochlorothiazide being doubled after 4 weeks if ‘control’ of BP (dBP 〈90 mmHg) was not achieved on the initial doses. Over the trial period of 8 weeks, felodipine reduced dBP from 102 to 85 mmHg and hydrochlorothiazide from 101 to 91 mmHg; the dBP reduction in the felodipine group was greater than that in the hydrochlorothiazide group (17 vs 9 mmHg) and the attained dBP lower in the felodipine group. About half of the patients in each group required the higher dose. Both regimes were effective and well tolerated. In the dosages used, felodipine was a slightly more effective antihypertensive drug than hydrochlorothiazide when added to metoprolol. There was no apparent difference in the tolerability of the two regimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061411
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  • 2
    Electronic Resource
    Electronic Resource
    Some factors associated with the use of the extractants 2% citric acid and 2% formic acid as estimators of available phosphorus in fertiliser products (1989)
    Springer
    Nutrient cycling in agroecosystems 19 (1989), S. 175-181 
    Details
    ISSN: 1573-0867
    Keywords: Chemical extractants ; solubility percentages ; impurity effects ; phosphate rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influences of calcium chloride, calcium sulphate, monocalcium phosphate, monosodium phosphate, calcium carbonate, sodium carbonate and iron and aluminium sulphates on the solubilities of two phosphate rocks (both ground and unground) in 2% citric and 2% formic acids have been examined. All of these potential ‘impurity’ elements can affect the solubility of the phosphate rock through a variety of mechanisms, including common ion effects, complexation, acid-base reactions and reduction. 2% formic acid solubilities were slightly more influenced by these effects than 2% citric acid figures, militating against the use of this extractant for assessing mixed component products at present being manufactured in New Zealand. Solid to solvent and P to solvent ratios were also found to affect the solubilities of raw phosphate rocks and a correction for the differences in total P content of the phosphate rocks to produce a consistent P to solvent ratio in solubility tests is suggested. This study has indicated that alternative methods for assessing phosphate rocks in admixture with other components should be examined in future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054459
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  • 3
    Electronic Resource
    Electronic Resource
    An investigation of extraction procedures for assessing the phosphate rock residue in multicomponent fertilisers (1993)
    Springer
    Nutrient cycling in agroecosystems 34 (1993), S. 223-231 
    Details
    ISSN: 1573-0867
    Keywords: alkaline ammonium citrate extraction ; extractable P distributions ; multicomponent fertilisers ; neutral ammonium acetate extraction ; neutral ammonium citrate extraction ; residue analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Five chemical extractants-water, neutral ammonium acetate, neutral ammonium citrate (hot and cold) and alkaline ammonium citrate-have been assessed on their ability to efficiently isolate the residual phosphate rock present in multicomponent fertilisers without affecting the phosphate rock. Phosphoric acid-based partially acidulated phosphate rocks (PAPRs) were manufactured along with several LONGLIFE (LL, single superphosphate to which “reactive” phosphate rock is added ex-den) materials for the assessment of these extractants. Each extractant was assessed by analysing the resultant residual phosphate rock isolated from each multicomponent fertiliser and comparing its chemical properties with the original phosphate rock used to manufacture the products. An analysis of “extractable phosphorus” was also undertaken. X-ray diffraction analysis was performed on selected phosphate rock residues as an independent method of examining the extraction techniques. Water and neutral ammonium acetate were found to be unsatisfactory for use as extractants; neither removed calcium sulphate when present, while the latter also did not appear to extract all the monocalcium phosphate component. The remaining three extractants all removed soluble phosphorus components and “impurity species” from the fertiliser products, leaving the residual phosphate rock relatively unaffected. Residue analyses were only slightly modified to those of the original rocks, although there were some inconsistencies in results obtained using hot neutral ammonium citrate. X-ray diffraction analysis showed no significant differences between residues produced from neutral ammonium citrate or alkaline ammonium citrate extractions, but water and neutral ammonium acetate residues confirmed the presence of calcium sulphate in LL and the presence of monocalcium phosphate in a neutral ammonium acetate extracted PAPR. From this study, cold neutral ammonium citrate and alkaline ammonium citrate appear to be equally suitable for isolating the phosphate rock from a multicomponent fertiliser, leaving the residual rock substantially unmodified from the original phosphate rock. However, there was a slight preference for cold neutral ammonium citrate due to its ease of preparation and use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750568
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical effects in commercial and laboratory mixtures of ‘reactive’ phosphate rock and acidulated fertilisers (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 111-118 
    Details
    ISSN: 1573-0867
    Keywords: Chemical analyses ; phosphate rock deactivation ; phosphate rock residue analysis ; single superphosphate—‘reactive’ phosphate rock mixtures ; partially acidulated phosphate rocks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The chemical analyses of different size fractions of a variety of commerical and laboratory prepared samples of partially acidulated phophate rocks and mixtures of ‘reactive’ phosphate rock and single superphosphate (called LONGLIFE in New Zealand) have been studied. Whereas only minor chemical segregation effects have been observed for partially acidulated products quite a large bias has been established for LONGLIFE materials, and more especially commercial samples, where larger proportions of phosphate rock were found in the lower size fractions. This inhomogeneity was considered to arise from poor mixing of components and subsequent inconsistent granulation; more stringent rejection criteria for undersize material would greatly assist in improving the product quality. Chemical ‘deactivation’ of the phosphate rock residue in LONGLIFE materials was also observed; this can be partially explained by a selective reaction of the ‘reactive’ phosphate rock component with acid still present at the time of mixing with the single superphosphate component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064233
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical effects in the assessment of phosphate rock residues extracted from multicomponent fertilisers (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 343-350 
    Details
    ISSN: 1573-0867
    Keywords: Partially acidulated phosphate rocks ; extraction methods ; solubility determinations ; contaminant effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Methods of obtaining “reactive” phosphate rock residues from multicomponent phosphate fertilisers which contain soluble phosphorus components have been examined. Extraction using cold neutral ammonium citrate has been found to be more suitable than water, as chemical reactions appear to occur in water extraction solutions to modify the residue, and more impurity species such as calcium sulphate and iron and aluminium phosphates remain in the residues to complicate the process of obtaining reliable solubility figures. “Deactivation” of the phosphate rock residues (as measured by decreased 2% formic acid solubilities) was found to be due to reactions occurring during the maturing process, and was dependent on the phosphate rock used, with North Carolina phosphate rock-based residues significantly affected, but Arad-based residues almost unaffected. However, for neutral ammonium citrate extractions, only North Carolina-based residues produced solubility figures lower than the original phosphate rock. Some selectivity of reaction in single superphosphate-“reactive” phosphate rock mixtures was indicated which further complicated assessment of the “deactivation” effect; however such an effect appeared to be much less significant than previously suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050372
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  • 6
    Electronic Resource
    Electronic Resource
    Evaluation of double extraction techniques as solubility tests for fertiliser products containing phosphate rock components (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 137-149 
    Details
    ISSN: 1573-0867
    Keywords: Extraction techniques ; partially acidulated phosphate rocks ; phosphate rock solubilities ; water solubilities ; neutral ammonium citrate solubilities ; 2% citric acid solubilities ; 2% formic acid solubilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Alternative extraction techniques for assessing the ‘available P’ content in multi-component fertilisers such as partially acidulated phosphate rocks have been examined. Two types of double extraction method have been investigated, one involving sequential extraction procedures, and a second examining both the initial fertiliser and its residue independently, using either water or cold neutral ammonium citrate as the first extractant, and either 2% citric or 2% formic acid as the second solvent. The latter method, which used cold neutral ammonium citrate as the initial extractant, produced the most consistent results and provided a reproducible assessment of the solubility of the phosphate rock residue; it was not obvious which second solvent was preferable. Comparisons between the original phosphate rocks and their extracted residues indicated that there were many subtle influences which affected the solubility of the phosphate rock components, but a general ‘deactivation’ of phosphate rock residues on acidulation as previously suggested was not apparent. Before any particular method can be recommended as an alternative to existing one step extraction techniques it is necessary to confirm its validity through agronomic trials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01063288
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