Technology and Engineering CHEMICAL ANALYSIS

Determination of nickel SMK Negeri 13 Bandung

Teknologi dan Rekayasa Bismillahirrahmanirrahiim  Rabbi zidna ilmaan ……..  Ya Allah, bukakanlah hati dan pikiran kami, terangi dengan cahaya-Mu. Anugrahkanlah setitik ilmu yang Engkau miliki kepada kami……  Ya Allah….. Perkenankanlah doa kami….

Objectives After this session, the students are expected to be able to: - explain the steps of determination of nickel - explain the objectives of every step - explain the function of reagents - arrange the planning of determination of nickel according to the job sheet - conduct the determination of nickel - do the calculation in the determination of nickel - arrange the report of the determination of nickel

Procedure  Weigh out accurately g of nickel sample salt. Rinse and pour into a 500 mL beaker provided with a clock glass cover and stirring rod.  Add 5 mL of dilute hydrochloric acid (1: 1) and dilute to 200 mL.  Heat the solution to O C, Teknologi dan Rekayasa

 hydrochloric acid (1: 1) : Suasana asam, kondisi optimum pra pengendapan, agar Ni(HDMG) 2 tidak langsung mengendap tetapi terbentuk secara perlahan saat pH dinetralkan secara perlahan juga sehingga ukuran partikel besar.  dilute to 200 mL, heat : kondisi optimum pengendapan Teknologi dan Rekayasa

 Add a slight excess of the dimethylglyoxime reagent ( mL) and immediately add dilute ammonia solution drop wise, directly to the solution and with constant stirring until precipitation takes place, and then in slight excess. dimethylglyoxime Teknologi dan Rekayasa

 slight excess (sedikit berlebih)  DMG tidak boleh terlalu berlebih karena DMG dilarutkan dalam alkohol. Jika terlalu berlebih, etanol akan melarutkan kembali Ni(HDMG) 2 sehingga endapan akan berkurang, (Pemisahan tidak sempurna) Teknologi dan Rekayasa

 DMG tidak boleh terlalu berlebih karena DMG dilarutkan dalam alkohol. Jika etanol terencerkan oleh air atau menguap, DMG akan mengkristal dan menambah berat endapan. (endapan tidak murni) Teknologi dan Rekayasa

Immediately (segera)  Mencegah proses “keluarnya” DMG dari larutan/mengkristal karena penguapan etanol dalam larutan panas.  Ammonia menaikkan pH Teknologi dan Rekayasa

directly to the solution…. Ni(HDMG) 2 mudah merambat naik pada dinding gelas kimia, maka pembentukannya tidak boleh terjadi pada dinding gelas tapi harus di tengah larutan Teknologi dan Rekayasa

 Filtering : pemisahan endapan dari sisa pereaksi dan pelarut  sintered-glass : media saring untuk zat yang tidak tahan panas/tidak akan dipanaskan lebih dari C  temperatur pemanasan Ni(HDMG) 2  Untuk ketelitian lebih tinggi : C Teknologi dan Rekayasa

 Wash the precipitate with cold water until free from chloride, and dry it at C for minutes.  Allow to cool in a desiccator and weigh. Repeat the drying until constant weight is attained.  Weigh as Ni(C4H 702N2)2  Calculate the percentage of nickel in the sample Teknologi dan Rekayasa

 cold water : memperkecil kelarutan  Tidak mungkin dicuci dengan larutan ion sejenis karena akan menambah berat endapan Teknologi dan Rekayasa

Discussion  Nickel is precipitated by the addition of an ethanolic solution of dimethylglyoxime CH 2 C(:NOH) 2 C(:NOH) 2 CH 2 referred to in what follows as H2DMG to a hot, faintly acid solution of the nickel salt, and then adding a slight excess of aqueous ammonia solution (free from carbonate). Teknologi dan Rekayasa

 The precipitate is washed with cold water and then weighed as nickel dimethylglyoximate after drying at C.  With large precipitates, or in work of high accuracy, a temperature of C should be used: any reagent that may have been carried down by the precipitate is volatilised.  Ni H 2 DMG  Ni(HDMG) 2 + 2H + Teknologi dan Rekayasa

The precipitate is soluble in: 1. free mineral acids (even as little as is liberated by reaction in neutral solution) 2. solutions containing more than 50 per cent of ethanol by volume, 3. hot water (0.6 mg per 100 mL), 4. Concentrated ammoniacal solutions of cobalt salts, Teknologi dan Rekayasa

The precipitate is insoluble in: 1. dilute ammonia solution, 2. solutions of ammonium salts 3. dilute acetic (ethanoic) acid-sodium acetate solutions. Teknologi dan Rekayasa

 Large amounts of aqueous ammonia and of cobalt, zinc, or copper retard the precipitation; extra reagent must be added, for these elements consume dimethylglyoxime to form various soluble compounds.  Better results are obtained in the presence of cobalt, manganese, or zinc by adding sodium or ammonium acetate to precipitate the complex;  iron(III), aluminium, and chromium(III) must be absent Teknologi dan Rekayasa

 Dimethylglyoxime forms sparingly soluble compounds with palladium,platinum, and bismuth.  Palladium and gold are partially precipitated in weakly ammoniacal solution;  In weakly acid solution palladium is quantitatively precipitated and gold partially.  Bismuth is precipitated in strongly basic solution Teknologi dan Rekayasa

 These elements, and indeed all the elements of the hydrogen sulphide group,should be absent.  Iron(II) yields a red-coloured soluble complex in ammoniacal solution and leads to high results if much of it is present.  Silicon and tungsten interfere only when present in amounts of more than a few milligrams.  Iron(III), aluminium, and chromium(III) are rendered inactive by the addition of a soluble tartrate or citrate, with which these elements form complex ions. Teknologi dan Rekayasa

 Dimethylglyoxime is almost insoluble in water, and is added in the form of a 1 per cent solution in 90% ethanol (rectified spirit) or absolute ethanol;  1 mL of this solution is sufficient for the precipitation of g of nickel.  As already pointed out, the reagent is added to a hot feebly acid solution of a nickel salt, and the solution is then rendered faintly ammoniacal. Teknologi dan Rekayasa

 This procedure gives a more easily filterable precipitate than does direct precipitation from cold or from ammoniacal solutions.  Only a slight excess of the reagent should be used, since dimethylglyoxime is not very soluble in water or in very dilute ethanol and may precipitate; if a very large excess is added (such that the alcohol content of the solution exceeds 50 per cent), some of the precipitate may dissolve. Teknologi dan Rekayasa

Thank You Teknologi dan Rekayasa