The identity of unknown C was narrowed down to a single compound by collecting the melting range of a compound consisting of unknown C and acetylsalicylic acid. melting point technique was also utilized to determine the purity of the pure sample of both which allowed for crystallization. A sufficient change in temperature that ultimately lowered the solubility allowed the formation of the crystalline solid in this experiment. 178 101 Irritant; Crystallization of Impure Compounds and Classification of Unknown by Melting Point Results and Discussion In this experiment, crystallization was conducted to purify an impure sample of sulfanilamide using a known solvent, 95% ethyl alcohol, and melting point technique was utilized to verify the purity of the final material. Freezing/Melting Point:163 - 167 deg C Decomposition Temperature:Not available. the crystal lattice. NIST Spectra Density: 1. It takes longer to melt solubility that occurred due to diffusion of the solvent will allow crystallization of the Melting Point Range of Pure Sample (C) 116-117. The furthest left side of the graph represents a sample that is pure compound "A," while the furthest right side of the graph represents a sample of pure compound "B." As the melting temperature does not rise above the eutectic temperature until the entirety of the impurity has melted, the quantity of impurity will determine how far the system will have progressed along the melting point line in the phase diagram before reaching the visible minimum of \(10\)-\(20\%\) of solid. Retrieved 5 May 2022. water, methyl alcohol, and toluene, were analyzed to determine the most appropriate solvent Through the crystallization of impure sulfanilamide and fluorene, pure sulfanilamide and fluorene was recovered. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Since the impurities are usually present in much smaller amounts than the compound being crystallized, most of the impurities will remain dissolved in the solvent even when it is cooled. % "R}~Q:~pgg'"l/O:OV~ @zo7g;)K;=d'}z8}7w7?Iuw?w~ikK^^'d4k;g_u_LOC6($uiz["Dw#d"egHf_O=4D~PD<.O3@MG_2)QZ>f.to_wv~} appropriate. So, the salt and ice form a salt water mixture which can be well below $\pu{32F}$, and so can cool to below $\pu{32F}$. The literature melting point of sulfanilamide is 164.5 - 166.5C. However, if the observed melting temperatures are outside of this range, then the compound is not pure. YuaoJ; ?,:kEC)61_\C4%kQ?(- YK'] [5][12][11], Sulfanilamide was first prepared in 1908 by the Austrian chemist Paul Josef Jakob Gelmo (18791961)[13][14] as part of his dissertation for a doctoral degree from the Technische Hochschule of Vienna. [5], Since sulfanilamide is used almost exclusively in topical vaginal preparations these days, adverse effects are typically limited to hypersensitivity or local skin reactions. Through crystallization of 0.746 g of fluorene using methanol as the solvent, 0.468 g of pure fluorene sample was extracted, with a 62.73% recovery as shown in Table 4. The purified substance can then be separated from the solvent and impurities by filtration. It is instructive to look at the structure of sulfanilamide and ask whether or not 95% ethyl alcohol should be a reasonable solvent for crystallizing this substance. Replacing broken pins/legs on a DIP IC package. also the first generation of antibiotics, used to treat many diseases. Give three reasons why the recovery was not 100%. Ref: MERCK INDEX 1976 Water Sol Estimate from Fragments: Wat Sol v1. The pure sample had a melting range of 162.9 C to 165.8 C while the impure sample had a melting range of 160.3 C to 163.2 C as shown in Table 1. Has 90% of ice around Antarctica disappeared in less than a decade? being left behind in the mother liquor and others were due to the use of too much solvent in Econ 1 - Chapter 1 Questions and Answers. There are several polar bonds in sulfanilamide, the NH and the SO bonds. This increases the purity of the melt, so the melting temperature increases somewhat. Although all samples start melting at the eutectic temperature, the first droplet of liquid is not seen until approximately \(10\)-\(20\%\) of the sample has microscopically melted. Differences between the impure sulfanilamide and the total weight i. For the ice cream making process, we start with pure ice and have the impurity in the liquid. OF3 rhe ethanol is heated to completely dissolve the sulfanilamide. Can archive.org's Wayback Machine ignore some query terms? It has a max of 255 and 312nm. This phenomenon is called crystallization if the crystal growth is relatively slow and selective or precipitation if the process is rapid and nonselective. nwC0\a`qPi+^9o}'w^OX"nlngH5wCF-?n&Tmc5{9 However, the melting point of impure sulfanilamide may be different due to the presence of impurities. Thanks for contributing an answer to Chemistry Stack Exchange! Introduction. While the pure sample lied within the primary melting range of sulfanilamide, there was a depression in the melting range of the impure sample because impurities disrupted the crystal lattice energies. With prior knowledge of the fact that like dissolves like. The solution discusses the crystallization of impure sulfanilamide using 95% ethyl alcohol. The paragraph is therefore a tad confusing. Percent Recovery 62% Melting Point Range of Pure Sample C 116-117. for the crystallization of an impure sample of or. Ref: Hansch,C et al. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? For example, if the melting point of a sample of sulfanilamide is significantly lower than the known melting point of pure sulfanilamide, it is likely that the sample is impure. nonhazard Compound B will continue to dissolve in the melt, until it reaches the eutectic composition (point a in Figure 6.7b), and the system will continue to melt at this composition until the entirety of the minor component (the impurity) is dissolved. This microscopic melting is not visible to the eye. Sulfanilamide (also spelled sulphanilamide) is a sulfonamide antibacterial drug. In many mixtures, the minimum melting temperature for a mixture occurs at a certain composition of components, and is called the eutectic point (Figure 6.7a). Melting point depression is the phenomenon of reduction of the melting point of a contaminated, impure material compared to the pure material. Melting point of impure sulfanilamide = 165.1 C Melting point of crystallised sulfanilamide = 163.0 C There is difference between melting points of crude and crystalline sulfanilamide that is because recrystallised product has a high purity or it doesn't have impurities and crude sulfanilamide or impure sulfanilamide has impurities in it. is a hazard so this is a concern. Sulfanilamide 163-166 Succinic acid 184-185 endobj As shown in Table 4, a pure sample collected through crystallization was relatively pure, with a melting range of 116.3C to 117.8C. The melting point of pure sulfanilamide is around 303-305C. the sample from its primary melting point range because impurities disrupted the energies in The first 5 pages are background explanation. In other words if you add salt to ice that is homogeneously right at the freezing point you won't get liquid water below zero because there is no where for the heat to flow. Percent Recovery 62% Melting Point Range of Pure Sample C 116-117. Whether a system is in fact pure, or sharply melting because it is at the eutectic composition, can be proven by performing a mixed melting point. ethanol. pure than the impure sample, but it is not certain whether it is 100% pure sulfanilamide. The paragraph is therefore a tad confusing. Compound Melting Range (C) stream Do I need a thermal expansion tank if I already have a pressure tank? By mixing ice with salt it takes heat from its surroundings this results in a lowering of the surrounding temperature. 163-164 C. % Once the minor component is completely dissolved, further melting continues of the bulk component. Sulfanilamide initially has a melting range of 163 to 166. consists of two covalently attached benzene rings, and as a result we closely resemble the It is important to accurately determine the melting point of a compound, especially in the pharmaceutical industry, to ensure the safety and effectiveness of the final product. Separately, add ~6 mL of 95% ethanol and your magnetic spin bar to your 50-mL Erlenmeyer flask. I need help on the last 3 pages. which signifies the presence of impurities within the mixture. zvG&ykc>E1F`T &q'w#4|]_"iSp:.CpZS$RiaGL.Fc}5x3n`"P&J+O4dA45,H(N;s:#0;GC In this experiment, crystallization was conducted to purify an impure sample of sulfanilamide using a known solvent, 95% ethyl alcohol, and melting point technique was utilized to verify the purity of the final material. See attached for full solution and proper format. The melting point of a compound is a measure of its purity. Melting point of impure sulfanilamide (should be a range): 157C - 160C Melting point of pure sulfanilamide: The literature (theoretical) melting point of pure sulfanilamide is 164.5C - 166.5C The experimental melting point of pure sulfanilamide is 162C - 164C Lab Report Guide: THIS IS DONE, RESULTS ARE ABOVE - 1. How can sodium chloride melt ice or keep it frozen? Crystallization methods are designed to A sufficient change in temperature that ultimately The melting point of a substance is often used to determine purity. However, the melting point of impure sulfanilamide may be different due to the presence of impurities. The first part of the experiment is the recrystallization of impure acetanilide. Mass of watch glass + Pure fluorene g 48. Listed below are solubility-vs-temperature data for an organic substance A dissolved in water. Melting point depression occurs due to the nature of a material's solid state. << /Length 11 0 R /Type /XObject /Subtype /Image /Width 378 /Height 484 /Interpolate When a compound is pure, its molecules are all arranged in an orderly, repeating pattern. Penatherene is highly nonpolar because of the absence of hetero atoms (N,O,S) and has The contrast in solubility at cold and warm temperatures is vital in the crystallization method. When \(10\)-\(20\%\) of solid has melted and a droplet is visible, the system may have progressed far from the eutectic composition (perhaps to begin visibly melting at point b in Figure 6.9a). Unknown C 138- If instead the solid has a significant amount of impurity, it may take melting of nearly \(10\%\) of the solid to fully dissolve the impurity, which means the melting temperature may not have progressed far from the eutectic temperature when a droplet becomes visible. the unknown sample is an impure version of the higher melting candidate. Most solids, such as ice, form as crystalline lattices of repeating ions or molecules. Benzoic acid is an aromatic carboxylic acid (Fig) which forms a colorless, crystalline solid and can be found naturally in both plants and animals and some microorganisms (del Olmo, 2017; Sandeepa, 2018). Introduction: [1] Powdered sulfanilamide was used by the Allies in World War II to reduce infection rates and contributed to a dramatic reduction in mortality rates compared to previous wars. ;fj ^U|Y_e,s#!f18p `g]mr}?R1 okvA. general technique involves dissolving the material to be crystallized in a hot solvent (or Enter salt. By comparing the solubility of impure fluorene in the 3 solvents in room temperature and in a hot water bath, the best solvent for the crystallization of impure fluorene was identified as methanol. [5], Solubility: One gram of sulphanilamide dissolves in approximately 37 ml alcohol or in 5 ml acetone. Thus ice problem when driving is solved (aside from the environmental concern of all the heavy salts). elimination, unknown C was identified as benzoin. experimental procedure for determining which one of three possible solvents is the most single compound by collecting the melting range of a compound consisting of unknown C Substance of higher latent heat of melting than water, similar melting point, Effect of inductive effect on boiling point,melting point and dipole movement. |(B8)[IqZ/gR 1%Q,#>Z;SstBnHs.pY'(k8Vjl[h /0uO *~#PTdkTK0H[3XQ_R1QH`;JCV4:ZHzbx4S0vg),+3 Finally, the The solid will continue melting until perhaps point c in Figure 6.9a, to give a relatively narrow melting range (between points b and c). solvent, fluorene will be highly soluble, even at room temperature. On May 18, 1909, Deutsches Reich Patentschrift number 226,239 for sulfanilamide was awarded to Heinrich Hrlein of the Bayer corporation. Report the melting points for both the impure sulfanilamide and the crystallized sulfanilamide and comment on the differences. { "6.1A:_Overview_of_Melting_Point" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.1B:_Uses_of_Melting_Points" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.1C:__Melting_Point_Theory" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.1D:__Step-by-Step_Procedures_for_Melting_Point_Determination" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.1E:_Mixed_Melting_Points" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()" }, { "6.01:_Melting_Point" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.02:_Boiling_Point" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.03:_Sublimation" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()", "6.04:_Chemical_Tests" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.b__1]()" }, [ "article:topic", "eutectic point", "eutectics", "freezing point depression", "authorname:nicholsl", "eutectic composition", "showtoc:no", "license:ccbyncnd", "licenseversion:40", "source@https://organiclabtechniques.weebly.com/" ], https://chem.libretexts.org/@app/auth/3/login?returnto=https%3A%2F%2Fchem.libretexts.org%2FBookshelves%2FOrganic_Chemistry%2FOrganic_Chemistry_Lab_Techniques_(Nichols)%2F06%253A_Miscellaneous_Techniques%2F6.01%253A_Melting_Point%2F6.1C%253A__Melting_Point_Theory, \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}}}\) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\), 6.1D: Step-by-Step Procedures for Melting Point Determination, Melting Point Depression (Lowering the M. P.), source@https://organiclabtechniques.weebly.com/, status page at https://status.libretexts.org. May cause respiratory tract irritation. xdWtsFK#l e[dIdVe J[a;o`*&0'UR7s[EDjUzb>m,o%{^[nkfn;m'v=?h-[^;5H5a]AgqIIzd~7TwA7sjsvr$;hgpn;kL;3Y}znvcg~/n6L/e{q.AwyO?t3W2z=^{\~/zqp0_0zEi~izz^Ui`R3/a"Xz.Vrk6An=UOgt|DAnQt!hhobJSkjv:J[v At the option of the instructor, turn in your crystallized material in a properly labeled container, Preparations. Expert Answer Melting point of impure sulfanilamide is lower than melting point of pure sulfa View the full answer produce a supersaturated solution that eventually forms crystals. However, the melting point of impure sulfanilamide may be different due to the presence of impurities. In part C, the melting point range of unknown C was compared to the melting points The dissolved material has a decreased. In part A, 0 g of impure sulfanilamide was crystallized and a pure sample of Mass of watch glass (g) 48. be 122 C as shown in Table 7. As solids are restricted in atomic motion, there is little difference in entropy between a pure and impure solid. In the old fashioned process, we used buttermilk sugar and a bit of vanilla. The difference between the phonemes /p/ and /b/ in Japanese. C to 139 C. melting range of sulfanilamide, there was a depression in the melting range of the impure Clothing: Wear appropriate protective clothing to prevent skin exposure. a certain solvent at a specific temperature or pressure. Sulfanilamide is a yellowish-white or white crystal or fine powder. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Also, compare these to the literature value. irritant. When an impure solid is warmed, microscopic melting first occurs in a pure region by the component with the lower melting point (compound A in Figure 6.7a). $ melting point technique was utilized to identify an unknown solid. The temperature is then slowly increased until the compound melts. health boiling point and then the solution is cooled to form the crystals of fluorene. Effect of impurities on melting point. Sulfanilamide is an organic sulfur compound structurally similar to p-aminobenzoic acid with antibacterial property.Sulfanilamide competes with PABA for the bacterial enzyme dihydropteroate synthase, thereby preventing the incorporation of PABA into dihydrofolic acid, the immediate precursor of folic acid.This leads to an inhibition of bacterial folic acid synthesis and de novo synthesis of . sample because impurities disrupted the crystal lattice energies. Why do impurities lower the melting point of an isolated substance? If unknown C was acetylsalicylic acid, then the melting It is for these reasons that a low melting range \(\left( < 2^\text{o} \text{C} \right)\) is associated with purity, although it is also possible that the solid's composition could be coincidentally near a eutectic point. In part A, 0 g of impure sulfanilamide was crystallized and a pure sample of 0 g was collected, with a 69% recovery of sulfanilamide as shown in Table 1. The melting point of the solid from the mother liquid was 162 -165, which is not the same as the crystallized material because the solid from the mother liquid may have traces of impurity which accounts for the melting point depression. sulfanilamide using a known solvent, 95% ethyl alcohol, and melting point technique was Unknown C by itself had a melting range of 138. stream In Part B, we will be Copyright 2023 StudeerSnel B.V., Keizersgracht 424, 1016 GC Amsterdam, KVK: 56829787, BTW: NL852321363B01. 122. Percent Recovery of Pure Fluorene through Crystallization and Melting Ranges of On the other hand, the solubility of a compound decreases as a solutions cool. Melting of a pure solid occurs at a higher temperature than melting of an impure solid, a concept called melting point depression (or freezing point depression). flammabili - Purify an impure sample of an antibiotic. Specifically in this The three solvents will illustrate three very different solubility behaviors: One of the solvents will be an appropriate solvent for crystallizing fluorene. Given Melting Ranges of Known Compounds, Unknown C (0.1 g) + Acetylsalicylic Acid (0.1 g), In this experiment, crystallization was conducted to purify an impure sample of, sulfanilamide using a known solvent, 95% ethyl alcohol, and melting point techni. My point is you actually WANT the ice to melt into a salt solution, because that will better cool the churn - as long as there's enough salt so that the liquid is cold enough. Answers/Comments are in blue ink. For example, a solid that is \(20\%\) compound A and \(80\%\) compound B would have a final melting temperature of point c in Figure 6.7b. This creates strong intermolecular forces, which give the compound a high melting point. [5], Sulphanilamide is contraindicated in those known to be hypersensitive to sulfonamides, in nursing mothers, during pregnancy near term and in infants less than 2 months of age. Weigh 0.3 g of impure sulfanilamide 1into your 25-mL Erlenmeyer flask. vtnnktVjRU4;jmT[JYm6*V,6VB7A^(eFYfZQkj"Br~V+jQKWZkhTr0~JW,R)W*EP|KB1S,FP?g ?^5me#IOy~xyl.&3T&dt2_l,dszeTL's|"mCn#md` nsfA^MhFvNyI ZpC-M=M&FQ(*fp8/)6m^s-Hja;@LNXt?rm{ Meaning a polar compound will On the other hand, the solubilit, lowered the solubility allowed the formation of the crystalline solid in t, terms of purifying an impure sample of a compound, crystallized molecules have a greater, initially existent in the compound in the mother liquor, Business Law: Text and Cases (Kenneth W. Clarkson; Roger LeRoy Miller; Frank B. Crystallization met, produce a supersaturated solution that eventually forms crystals. Table 4. This is true for several reasons: experimental loss, the original sample is not 100% sulfanilamide, and some sulfanilamide is soluble in the solvent even at 0 C. So, this wouldn't work. Some sources of sample loss of the sulfanilamide always select a solvent such that the boiling point of solvent is lower than the melting organic compounds from a mixture of compounds we are given a chemical in liquid 2A)1 Color of impure sulfanilamide: yellowish whitish powder-Color of pure sulfanilamid View the full answer Transcribed image text: 1. The purity of the sample collected at the end of crystallization was confirmed through the measurement of the melting points of the pure and impure samples of sulfanilamide. Also, compare these to the literature value. I need help on the last 3 pages. . It would not have been possible to recover all of the product because the Try it at home Mixing salt will result in liquid water that can stay liquid below $0^oC$. Physical and chemical properties Physical State Solid Appearance Off-white Odor Odorless Odor Threshold No information available pH 5.8-6.1 0.5% aq. It is important to accurately determine the melting point of a compound, as it can be used to identify and distinguish different compounds. The recorded melting range for this system would be at the maximum between temperatures a and c, but if the first droplet is seen at point b, the recorded melting range would be between temperatures b and c. A melting point is a useful indicator of purity as there is a general lowering and broadening of the melting range as impurities increase. The melting point of the solid from the mother liquid was 162 -165, which is not the same as the crystallized material because the solid from the mother liquid . The pH of a 0.5% aqueous solution of Sulfanilamide is 5.8 to 6.1. << /Type /Page /Parent 3 0 R /Resources 6 0 R /Contents 4 0 R /MediaBox [0 0 612 792] In Part C of this experiment, we will determine the identity of an. in this experiment we will get introduced to the technique of crystallization, In part A of this experiment we will carry out a crystallization of impure, crystallization will be used to purify the desired compound and isolate solid, Variations in Psychological Traits (PSCH 001), Expanding Family and Community (Nurs 306), American Politics and US Constitution (C963), Health Assessment Of Individuals Across The Lifespan (NUR 3065L), Leadership and Management in Nursing (NUR 4773), Creating and Managing Engaging Learning Environments (ELM-250), Professional Application in Service Learning I (LDR-461), Advanced Anatomy & Physiology for Health Professions (NUR 4904), Principles Of Environmental Science (ENV 100), Operating Systems 2 (proctored course) (CS 3307), Comparative Programming Languages (CS 4402), Business Core Capstone: An Integrated Application (D083), Lesson 6 Plate Tectonics Geology's Unifying Theory Part 2. Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Biphenyl. If absorbed, systemic side effects commonly seen with sulfanilamides may occur. flammable, O-toluic acid (CH 3 )C 6 H 4 ( Therefore ethyl alcohol since they have similar polarities. Instead think about what happens if you add an impurity to the water and it reduces the melting point way down to -22 C as was given in your textbook. Melting of an impure solid into an impure liquid therefore has a larger change in entropy than melting a pure solid into a pure liquid (Figure 6.8a). solubility at lower temperatures and will separate from the solution as it is cooled. compounds that melt over a wide range are assumed to be relatively impure. The melting point technique was useful in this sense because if the pure sample extracted from crystallization was pure, the melting point of the sample lied within its primary melting point range. Temperature Solubility of A in C 100 mL of water g 0 1. 4 0 obj To use this instrument, a small amount of the compound is placed in a capillary tube, which is then inserted into the apparatus. Determine the melting point for number 1 and number 2 of 2b Show transcribed image text Expert Answer Transcribed image text: 1. I hope you get it. dissolve in polar solvent like water while non polar compounds will dissolve in nonpolar recovered. : an American History (Eric Foner), Forecasting, Time Series, and Regression (Richard T. O'Connell; Anne B. Koehler), Brunner and Suddarth's Textbook of Medical-Surgical Nursing (Janice L. Hinkle; Kerry H. Cheever), Campbell Biology (Jane B. Reece; Lisa A. Urry; Michael L. Cain; Steven A. Wasserman; Peter V. Minorsky), Psychology (David G. Myers; C. Nathan DeWall), Chemistry: The Central Science (Theodore E. Brown; H. Eugene H LeMay; Bruce E. Bursten; Catherine Murphy; Patrick Woodward), Lecture notes, lecture all - Chapter 15-20, Determination of the Alcohol Content of Wine by Fractional Distillation Lab Report, Study Guide for Exam #1 Chapter 1- 4 for ECON 2. comparable melting points when each is pure, provides a useful laboratory technique. a. Crystallization is a method of separation centered on the reduced solubility of a compound in