Gravimetric Determination of Phosphorus in Fertilizer Samples Essay

I. AbstractThe purpose of this experimentation is to figurethe Phophorus satisfy of fertiliser samples exploitation Gravimetric Analysis. It involves dissolution of the plant food sample, precipitation and heating and cooling of the sample. Pooled modular deviations of the two entropy sets for % Pwet, %P teetotal, %P2O5 wet and %P2O5 dry were 5.1448, 5.1472, 11.8436 and 11.8504 respectvely. During the experiment a data rejection for %P and %P2O5 was concluded at approximately 20% and 47%. finale of the Phosphorus content in fertilizer is vital in graphic symbol assurance and in the choosing of a fertilizer grade important for agriculture.II. admission make ups require essential nutrients such as Nitrogen, Phosphorus, Potassium or southward to grow. However, most soils lack these macronutrients indeed a decrease in solid food mathematical production. In connection with this, the use of fertilizers containing these macronutrients has been part of the agricultural tradition . Fertilizers have in its labels a set of get alongs, known as the fertilizer grade that evermore appear in the form N-P-K, indicates the proportions of essential nutrients present (ie 10-10-10 which promoter 10% Nitrogen, 10% Phosphate in the form of P2O5, 10% Potassium in the form of K2O).Different organizations worldwide like Association of Ameri butt joint Plant Food Control Officials (AAPFCO) in the United States, conduct different tests to appraise the accuracy and consistency of the nutrient content with regards to that of the product label and as well as to ensure quality assurance as part of consumer rights. Analysis of fertilizer bum be conducted using Gravimetric Analysis.In Gravimetric Analysis, the product with known theme is resulted from the conversion of the analyte to a meltable pass that can be easily deformed and is free from impurities by subjecting it to heat. This product of known composition pull up stakes then be weighed and the percentage of the a nalyte in the sample can be determined. In this experiment, the analyte, Phosphorus in the fertilizer depart be descendd as Magnesium Ammonium Phosphate Hexahydrate, MgNH4PO4 ( 6H2O5H2O + HPO42- + NH4+ + Mg2+ + OH- ( MgNH4PO4 ( 6H2O (s) (1)The purpose of this experiment is to determine the percentage of Phosphorus (P) and Diphosphorus (P2O5) in the fertilizer sample by the means of Gravimetric Analysis.III. data and ResultsIn this experiment, the wet (as received) and dry weights of the fertilizer sample, produceed from the former experiment of moisture determination of the same fertilizer sample were employ. Weights were split into two data sets, Data pot 1 having four (4) trials and Data Set 2 having three (3) trials.The change sample from the introductory experiment from which moisture was determined, was dissolved and is converted into a sparingly soluble f any, MgNH4PO4 ( 6H2O which is then riddleed and weighed. The percolate motif used was weighed to easily deter mine the weight of the precipitate. The precipitate was then dried and weighed.IV. DiscussionThis experiment aims to determine the percentage of P and P2O5 in fertilizer sample using Gravimetry. The fertilizer sample from the previous experiment of Moisture Determination was utilized in this experiment. The dried fertilizer sample was dissolved with 40 mL distilled weewee and was then separateed to obtain a clear filtrate.In Gravimetry, it is important to use a effect agent that if not item, should be selective and would give out a precipitate containing the analyte. This set up agent should also give out a precipitate that is easily filtered and process from impurities, unreactive with the elements present in the atmosphere, of poor solubility to lessen the loss of analyte during filtration and washing, and with known composition after drying or heating. In this case, 45 mL of 10% MgSO4 ( 7H2O was added to the filtrate, with 150 mL 2M NH3 as the set up agent to obtain the desired precipitate MgNH4PO4 ( 6H2O which contains the analyte P. See equation 1. While opposite effectuate agent like NH4Cl can be used, NH3 was used otherwise to ensure that the desired precipitate would be form. The social movement of Cl- ions will more likely to attract Mg2+ thus producing MgCl2 precipitates, which do not contain the analyte in this experiment which is P.It should be noted that NH3 is added slowly with regular stirring to the solution to ensure the exploitation of the precipitate, resulting to a precipitate that is easier to filter and be freed of impurities. This technique is related to the von Weirmans ratio wherein the particle size of it of it of a precipitate is inversely proportional to the value of Relative Superaturation presumption byRelative Supersaturation = picWhereQ= concentration of reactants before precipitationS= solubility of the precipitatePrecipitates are either formed by nucleation, or by particle growth. In nucleation, particles jo in together to form a bountiful mass, usually a result of supersaturation in solutions. It consists of huge heart of precipitate, however, is make up of small particles that are hard to filter. In this experiment, what is desired is particle growth that yields a precipitate of large size but of smaller number. This is doable by further precipitation wherein particles amaze to the progress of initially turn particles. The supersaturation state of the solution is eased during constant stirring upon addition of the precipitating agent, thus promoting particle growth rather nucleation. With respect to the von Weirmans ratio, the high up the value of the ratio, the higher the possibility of getting smaller particles, thereby promoting nucleation, impertinent to a lower value of the ratio which promotes particle growth that will yield larger precipitates that is important in this experiment.After the addition of the precipitating agent with constant stirring, the mixture was allo wed to stand at room temperature for 15 mins. It is important to let the mixture stand, without any agitation or extraneous forces acting on it to let digestion to occur. Digestion is necessary to allow reprecipitation, wherein particles will adhere to the initially small precipitates, and to expel water molecules thus lessening the surface area available for adsorption which causes impurities to obtain larger particles with greater virtue and easier filterability.After 15 mins, the mixture was filtered using the preweighed filter paper. The filter paper that was preweighed was kept in the dessicator until further use to keep the moisture from adhering to the filter paper. Preweighing the filter paper was helpful for easy determination of the weigth of the precipitate. During filtration, precipitate was washed with distilled water in small portions of 5mL twice. For each washing, the distilled water was poured into the beaker where precipitation occured to squirrel away the remain ing precipitates that adhered to the sides of the beaker.After washing with distilled water, two 10mL portions of 95% ethanol were used for second washing. The use of 95% ethanol, becaue of its volatility thus will dry the precipitate faster, will ensure that no more water is trap in the pores between the precipitates, minimal solubility loss and particles of small size will not loosen up and pass through the pores of the filter paper. Smaller portions of the wash liquid were used to ensure that the precipitate will still be intact and nosignificant loss in the amount of the precipitate due to the overflowing of washes liquid.The filter paper containing the precipitate was then alter inside the oven set a t 110C for 1 hour and was cooled in a dessicator for 15 min. After this, the weight of the precipitate was determined by subtracting the value of the preweighed filter paper with the weight of the filter paper including the precipitate.Even though Gravimetry is considered as one o f the businesslike and less expensive ways of determining a fertilizer component, this technique is still not fool proof and errors due to authoritative and enigmatic factors may lead to an erroneous result. One of these errors is the fast addition of the precipitating agent and low impact of agitation that leads to the production of larger amount of small particles that may pass through the filter paper thus having lesser amount of precipitate, and a lower value for the P or P2O5 content in the sample. On the other hand, since while the mixture stands in room temperature without any coverings, contaminants like dust particles may be include in the mixture, contributing weight to the precipitate, giving a higher yield. This high yield will give a P or P2O5 content of the sample higher than its actual value.It can be observed from remit 3 that the range of % P and % P2O5 lies between approximately 6% to 13% and 15% to 30% respectively with 20% and 47% suspicious set since it is almost double of the determine in range. By performing the Q test, the determine were confirmed to be accpetable with regards to the actual value and determine in the population, or rejected. get across 4.1 and 4.2 shows the values that were rejected and accepted for each data set. reflexion that the 20% and 47% for % P and % P2O5 respectively, both belonging to Data Set 1 were rejected with 95% confidence level, meaning that the Qexp exceeded the value of the Qtabulated.Of all the trials in both Data Set 1 and 2, the group with values similar to that of the rejected values were the ones who obtained the greatest amount of precipitate. See Table 2. This rejection or errounous error in the data can be attributed to the determinate and indeterminate errors in the experiment. One more error that could be the tenableness for this rejection is the personal error in terms of the reading of the analytical balance. Also, because of this rejection in data, aside from the fact that Data Set 2 has lower number of population, Data Set 2 parameters for Measure of Precision are scalelike to each other, with the dried samples having greater values than that of the wet sample. Iti s because dried sample are purer than that of the wet sample containing still moisture and other interfering agent to getting the actual % P and % P2O5.V. Summary and ConclusionsIn this experiment, it was determined that the fertilizer sample has % P range of 6% to 13% with % P2O5 from 15% to 30%. However, the usual types of fertilizers with phosphates contain a minimum of 42.5 % water soluble phosphate and 46% total phosphate by weight, as in the case of Triple Superphosphate or 85 % water soluble and 20% available in Superphosphate. It should be noted that the theoretical values will vary depending on the type of fertilizer used in the experiment.Despite the data rejection that occurred, overall, it can be said that the experiment is a success since the objectives of the experiment such as performing gravimetric summary in the determination of phosphorus content and to know the principle in separation by precipitation were achieved.Yet, it is recommended that there would be a specific manner of putting the precipitating agent, like addition dropwise or true amounts per second or stirring so as to ensure the veracious formation of crystals needed by the experiment. It should also be observed that upon digestion, or letting the mixture stand without agitation, the mixture should be covered to reduce impurities present in the atmosphere.VI. ReferencesChapter 3 Gravimetry. California State University, Dominguez Hills. < http//www.csudh.edu/oliver/che230/textbook/ch03.htm> Accessed 17 January 2013.Fischer, R.B. and Peters, D.G. Quantitative Chemical Analysis 3rd ed. 1968 pp42-4349Food and husbandry Organization of the United Nations. AGP Fertilizer Specifications. http//www.fao.org/agriculture/crops/core-themes/theme/spi/plantnutrition/fertspecs/en/. Accessed 04 January 2013.Rehm, G. et al. appreciation Phosphorus Fertilizers Phophorus in the Agricultural Environment. University of Minnesota Extension. 2010. < http//www.extension.umn.edu/distribution/cropsystems/dc6288.html> Accessed 17 January 2013.Skoog, D. et al. rudiments of Analytical Chemistry 6th ed. Saunder College Publishing. 1992 pp72-80