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Senin, 20 Februari 2012
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Bioetanol dari air kelapa Semakin mahalnya minyak tanah non subsidi, berdampak positif bagi berkembangnya kreatifitas masyarkat. Berbagai upaya dalam mencari bahan bakar murah sebagai pengganti minya bumi, bermunculan. Terobosan pemanfaatan berbagai bahan alternatif pun banyak ditemukan. Mulai dari biogas sebagai pengganti penggerak genset, sampai pemanfaatan limbah air kelapa disulap menjadi biotanol pengganti minyak tanah. Menurut Imam Suhadi, bioetanol memiliki beberapa keunggulan, dibanding minyak tanah. Selain ramah lingkungan, penggunaan bioetanol tidak menyebabkan kompor meledak dan sangat aman. Hanya, untuk memanfaatkan energi alternatif yang murah ini harus menggunakan kompor sumbu secara khusus. Dan kompor khusus ini sudah banyak di pasar. Terutama di wilayah Karanganyar dan Sukoharjo Jawa Tengah. Untuk DIY, seperti belum banyak tahu teknologi ini, sehingga pemanfaatannya masih relatif sedikit dan terbatas. Dengan menggunakan alat penyulingan hasil modifikasi sendiri, Hadi begitu panggilan akrab bapak 4 anak ini melakukan serangkaian ujicoba dan hasilnya ternyata di luar dugaannya. Dari 200 liter limbah air kelapa ternyata menghasilkan tidak kurang dari 90 liter bioetanol. Di samping memanfaatkan limbah air kelapa, Hadi juga memanfaatkan nira kelapa atau legen sebagai bahan pembuatan bietanol berkadar 90 persen yang biasa diperguankan untuk keperluan kesehatan di rumah sakit. Sebagai pencuci dan sterilisasi alat-alat medis. “Untuk bioetanol kadar 90 persen, hanya melayani permintaan suplier perlengkapan alat kesehatan,” kata Hadi yang mengaku hanya tamatan SLTA ini. Secara umum, cara pembuatan bioetanol berbahan limbah air kelapa dengan legen memiliki kesamaan proses. Hanya saja pada modal produksi yang agak beda kalkulasinya. Limbah air kelapa harganya relatif murah. Hanya Rp. 400 per liter. Sedangkan untuk harga legen per liter kisaran Rp. 2 ribu. Bahkan kadang Rp. 3 ribu. Hal ini lantas berpengaruh pada harga jual. Bioetanol berbahan limbah air kelapa yang memiliki kadar etanol 70 persen biasa dijual Rp. 7 ribu perliter. Sedangkan bioetanol dari legen berkadar 90 persen, Rp. 20 ribu per liter. Untuk mendapatkan bioetanol berkadar 90 persen harus dilakukan langkah dua kali penyulingan. Proses Sebelum proses penyulingan, bahan baku yang berupa air kelpa maupun legen terlebih dahulu di fermentasi selama 70 jam. Pada proses fermentasi ini ada beberapa bahan tambahan seperti ragi yang dimauskkan ke dalam tampungan, lantas ditutup sampai proses fermentasi itu terjadi. Setelah lebih kurang 3 hari, baru proses penyulingan dilakukan. Dengan memasukkan bahan ke dalam drum dan dipanasi sampai mencapai 80 derajat celcius. Biasanya pada angka ini uap air, sudah mulai naik. Dan proses ini dipertahankan sampai 5 hingga 7 jam. Untuk 200 liter air kelapa bisa menghasilkan tidak kurang dari 90 liter bioetanol dengan kadar 70 persen, sedangkan untuk bahan dari legen setiap 200 liternya bisa menghasilkan tidak kuran dari 110 liter bioetanol dengan kadar 70 persen. Untuk mendapatkan Bioetanol 90 persen maka dilakukan penyulingan lagi dengan alat yang lebih kecil. “Alat ini memang belum sempurna. Masih perlu dimodifikasi. Semakin panjang pipa distilator, hasilnya akan lebih bagus,” papar Hadi yang juga sebagai pengusaha jasa mebel air. Untuk membuat alat ini dia mengaku hanya merogoh kocek Rp. 4 juta. Jika dibanding alat buatan pabrik, seharga Rp. 12 juta lebih, alat modifikasi Hadi ini memang sangat sederhana. Meski begitu, secara konsep destilasi sudah bisa diandalkan. Selama ini untuk proses penyulingan dia memanfaatkan limbah gergaji sebagai bahan bakarnya, menurut Hadi. Permintaan pasar cukup bagus, untuk memenuhi permintaan pasar dia sudah lakukan produksi. Meski masih kecil-kecilan, karena terbentur permodalan. Dia berharap bisa lebih besar memproduksi bioetanol pengganti minyak tanah. Prospeknya sangat bagus. Menurutnya sisa dri proses penyulingan ini ternyata juga dapat dimanfaatkan untuk bahan dasar pupuk cair dan pupuk padat organik. Dia sudah buktikan untuk kebun salak pondohnya, dan hasilnya cukup memuaskan. http://id.shvoong.com/business-management/business-ideas-andopportunities/2183557-cara-menyulap-limbah-menjadi-minyak/#ixzz1ffHWUnQp
Diposting oleh aulia noviyanti bandar lampung 2/20/2012 08:55:00 PM
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KEGUNAAN ENZIM DALAM BEBERAPA BIDANG INDUSTRI 1. Industri Deterjen
Rekayasa versi tradisional enzim untuk produksi deterjen adalah, protease dan amilase. Kompatibilitas enzim dengan deterjen (yaitu sifat stabilitasnya) diutamakan, sehingga kemampuannya untuk berfungsi pada suhu yang lebih rendah juga memberikan peningkatan, untuk menghemat energi, temperatur yang digunakan dalam pencucian rumah tangga dan mesin pencuci piring otomatis telah diturunkan pada tahun ini. 2. Enzim Untuk Konversi Pati
Konversi enzimatik pati oleh jagung untuk sirup fruktosa adalah bioproses yang menakjubkan. Langkah pertama dalam proses ini adalah konversi pati untuk oligomaltodextrins oleh aksi amilase. Sekarang amilase dengan sifat yang dioptimalkan, seperti peningkatan stabilitas termal, toleransi asam, dan kemampuan untuk digunakan tanpa penambahan kalsium. 3. Produksi Bahan Bakar Alkohol
Selama beberapa dekade terakhir, telah terjadi peningkatan minat penggunaan bahan bakar alcohol yang diakibatkan oleh kenaikan minyak mentah dunia dan kerusakan lingkungan. Oleh karena itu, saat ini dilakukan upaya penting untuk mengembangkan enzim yang menggunakan substrat seperti lignoselulosa, untuk membuat bio-ethanol lebih kompetitif dengan bahan bakar fosil. Biaya enzim yang dibutuhkan untuk mengubah lignoselulosa menjadi materi yang cocok untuk fermentasi merupakan masalah besar, sehingga penelitian difokuskan pada pengembangan enzim dengan aktivitas tinggi dan stabilitas yang baik. 4. Tekstil Aplikasi
Dalam industri tekstil penggunaan enzim merupakan sesuatu yang baru. Proses berbasis enzim banyak dilakukan sehingga menggunakan sedikit air dan energi, kini telah dikembangkan berdasarkan lyase pectate. sehingga dampak positif lingkungan dari proses ini diakui oleh masyarakat luas. 5. Enzim Untuk Industri Pakan
Sebagai contoh, xylanases dan glucanases telah digunakan beberapa dekade terakhir ini. Pada pakan berbasis sereal untuk hewan monogastric, memanfaatkan tanaman berbasis feed berisi selulosa dengan jumlah besar dan hemiselulosa. Selama beberapa tahun terakhir penelitian difokuskan pada pemanfaatan fosfor alam yang terikat dalam asam fitat. Pendekatan alternatif untuk pengembangan enzim sehingga lebih efektif telah meningkatkan aktivitas katalitik phytases jamur oleh situs directed mutagenesis. 6. Enzim Untuk Industri Makanan Baru-baru ini, banyak penelitian telah dilakukan pada aplikasi dari transglutaminase sebagai agen texturing dalam memproses misalnya, mie sosis, dan yoghurt. Hambatan yang mungkin mencegah penggunaan yang lebih luas, adalah terbatasnya ketersediaan enzim dalam skala industri pada saat ini. Penggunaan klarifikasi lakase dari jus (laccases mengkatalisis dan menghubungkan lintas dari polifenol, yang mengakibatkan penghapusan polifenol oleh filtrasi yang mudah) dan untuk rasa perangkat tambahan dalam bir ditetapkan aplikasi baru dalam industri minuman. 7. Pengolahan Lemak dan Minyak
Dalam industri lemak dan minyak, beberapa enzim baru saja diperkenalkan. Meskipun penggunaan lipase amobil dalam interesterifikasi dari trigliserida pertama kali dijelaskan pada 1980-an, prosesnya belum cukup efektif. Meskipun produksi enzim telah menjadi jauh lebih efisien, biaya imobilisasi tetap terkendala. Sebuah proses baru untuk immobilisasi lipase berdasarkan granulasi silika telah secara dramatis menurunkan biaya proses, dan prosedur berdasarkan materi baru sekarang sedang diimplementasikan untuk produksi com- modity lemak dan minyak tanpa kandungan asam lemak-trans. Diposting oleh aulia noviyanti bandar lampung 2/20/2012 08:51:00 PM
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Sleeping beauty A long time ago there were a king and queen who were unhappy because they were childless. But it happened that once when the queen was bathing, a frog crept out of the water on to the land, and said to her, "Your wish shall be fulfilled, before a year has gone by, you shall have a daughter." What the frog had said came true, and the queen had a little girl who was so pretty that the king could not contain himself for joy, and ordered a great feast. He invited not only his kindred, friends and acquaintances, but also the wise women, in order that they might be kind and well disposed towards the child. There were thirteen of them in his kingdom, but, as he had only twelve golden plates for them to eat out of, one of them had to be left at home. The feast was held with all manner of splendor and when it came to an end the wise women bestowed their magic gifts upon the baby - one gave virtue, another beauty, a third riches, and so on with everything in the world that one can wish for. When eleven of them had made their promises, suddenly the thirteenth came in. She wished to avenge herself for not having been invited, and without greeting, or even looking at anyone, she cried with a loud voice, "The king's daughter shall in her fifteenth year prick herself with a spindle, and fall down dead." And, without saying a word more, she turned round and left the room. They were all shocked, but the twelfth, whose good wish still remained unspoken, came forward, and as she could not undo the evil sentence, but only soften it, she said, it shall not be death, but a deep sleep of a hundred years, into which the princess shall fall. The king, who would fain keep his dear child from the misfortune, gave orders that every spindle in the whole kingdom should be burnt. Meanwhile the gifts of the wise women were plenteously fulfilled on the young girl, for she was so beautiful, modest, good-natured, and wise, that everyone who saw her was bound to love her. It happened that on the very day when she was fifteen years old, the king and queen were not at home, and the maiden was left in the palace quite alone. So she went round into all sorts of places, looked into rooms and bed-chambers just as she liked, and at last came to an old tower. She climbed up the narrow winding staircase, and reached a little door. A rusty key was in the lock, and when she turned it the door sprang open, and there in a little room sat an old woman with a spindle, busily spinning her flax. "Good day, old mother," said the king's daughter, "what are you doing there?" "I am spinning," said the old woman, and nodded her head. "What sort of thing is that, that rattles round so merrily," said the girl, and she took the spindle and wanted to spin too. But scarcely had she touched the spindle when the magic decree was fulfilled, and she pricked her finger with it. And, in the very moment when she felt the prick, she fell down upon the bed that stood there, and lay in a deep sleep. And this sleep extended over the whole palace, the king and queen who had just come home, and had entered the great hall, began to go to sleep, and the whole of the court with them. The horses, too, went to sleep in the stable, the dogs in the yard, the pigeons upon the roof, the flies on the wall, even the fire that was flaming on the hearth became quiet and slept, the roast meat left off frizzling, and the cook, who was just going to pull the hair of the scullery boy, because he had forgotten something, let him go, and went to sleep. And the wind fell, and on the trees before the castle not a leaf moved again. But round about the castle there began to grow a hedge of thorns, which every year became higher, and at last grew close up round the castle and all over it, so that there was nothing of it to be seen, not even the flag upon the roof. But the story of the beautiful sleeping Briar Rose, for so the princess was named, went about the country, so that from time to time kings' sons came and tried to get through the thorny hedge into the castle. But they found it impossible, for the thorns held fast together, as if they had hands, and the youths were caught in them, could not get loose again, and died a miserable death. After long, long years a king's son came again to that country, and heard an old man talking about the thorn hedge, and that a castle was said to stand behind it in which a wonderfully beautiful princess, named Briar Rose, had been asleep for a hundred years, and that the king and queen and the whole court were asleep likewise. He had heard, too, from his grandfather, that many kings, sons had already come, and had tried to get through the thorny hedge, but they had remained sticking fast in it, and had died a pitiful death. Then the youth said, "I am not afraid, I will go and see the beautiful Briar Rose." The good old man might dissuade him as he would, he did not listen to his words. But by this time the hundred years had just passed, and the day had come when Briar Rose was to awake again. When the king's son came near to the thorn hedge, it was nothing but large and beautiful flowers, which parted from each other of their own accord, and let him pass unhurt, then they closed again behind him like a hedge. In the castle yard he saw the horses and the spotted hounds lying asleep, on the roof sat the pigeons with their heads under their wings. And when he entered the house, the flies were asleep upon the wall, the cook in the kitchen was still holding out his hand to seize the boy, and the maid was sitting by the black hen which she was going to pluck. He went on farther, and in the great hall he saw the whole of the court lying asleep, and up by the throne lay the king and queen. Then he went on still farther, and all was so quiet that a breath could be heard, and at last he came to the tower, and opened the door into the little room where Briar Rose was sleeping. There she lay, so beautiful that he could not turn his eyes away, and he stooped down and gave her a kiss. But as soon as he kissed her, Briar Rose opened her eyes and awoke, and looked at him quite sweetly. Then they went down together, and the king awoke, and the queen, and the whole court, and looked at each other in great astonishment. And the horses in the courtyard stood up and shook themselves, the hounds jumped up and wagged their tails, the pigeons upon the roof pulled out their heads from under their wings, looked round, and flew into the open country, the flies on the wall crept again, the fire in the kitchen burned up and flickered and cooked the meat, the joint began to turn and sizzle again, and the cook gave the boy such a box on the ear that he screamed, and the maid finished plucking the fowl. And then the marriage of the king's son with Briar Rose was celebrated with all splendor, and they lived contented to the end of their days. Diposting oleh aulia noviyanti bandar lampung 2/20/2012 08:48:00 PM
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Beauty and the beast
Once upon a time as a merchant set off for market, he asked each of his three daughters what she would like as a present on his return. The first daughter wanted a brocade dress, the second a pearl necklace, but the third, whose name was Beauty, the youngest, prettiest and sweetest of them all, said to her father: "All I'd like is a rose you've picked specially for me!" When the merchant had finished his business, he set off for home. However, a sudden storm blew up, and his horse could hardly make headway in the howling gale. Cold and weary, the merchant had lost all hope of reaching an inn when he suddenly noticed a bright light shining in the middle of a wood. As he drew near, he saw that it was a castle, bathed in light. "I hope I'll find shelter there for the night," he said to himself. When he reached the door, he saw it was open, but though he shouted, nobody came to greet him. Plucking up courage, he went inside, still calling out to attract attention. On a table in the main hall, a splendid dinner lay already served. The merchant lingered, still shouting for the owner of the castle. But no one came, and so the starving merchant sat down to a hearty meal. Overcome by curiosity, he ventured upstairs, where the corridor led into magnificent rooms and halls. A fire crackled in the first room and a soft bed looked very inviting. It was now late, and the merchant could not resist. He lay down on the bed and fell fast asleep. When he woke next morning, an unknown hand had placed a mug of steaming coffee and some fruit by his bedside. The merchant had breakfast and after tidying himself up, went downstairs to thank his generous host. But, as on the evening before, there was nobody in sight. Shaking his head in wonder at the strangeness of it all, he went towards the garden where he had left his horse, tethered to a tree. Suddenly, a large rose bush caught his eye. Remembering his promise to Beauty, he bent down to pick a rose. Instantly, out of the rose garden, sprang a horrible beast, wearing splendid clothes. Two bloodshot eyes, gleaming angrily, glared at him and a deep, terrifying voice growled: "Ungrateful man! I gave you shelter, you ate at my table and slept in my own bed, but now all the thanks I get is the theft of my favorite flowers! I shall put you to death for this slight!" Trembling with fear, the merchant fell on his knees before the Beast. "Forgive me! Forgive me! Don't kill me! I'll do anything you say! The rose wasn't for me, it was for my daughter Beauty. I promised to bring her back a rose from my journey!" The Beast dropped the paw it had clamped on the unhappy merchant. "I shall spare your life, but on one condition, that you bring me your daughter!" The terror-stricken merchant, faced with certain death if he did not obey, promised that he would do so. When he reached home in tears, his three daughters ran to greet him. After he had told them of his dreadful adventure, Beauty put his mind at rest immediately. "Dear father, I'd do anything for you! Don't worry, you'll be able to keep your promise and save your life! Take me to the castle. I'll stay there in your place!" The merchant hugged his daughter. "I never did doubt your love for me. For the moment I can only thank you for saving my life." So Beauty was led to the castle. The Beast, however, had quite an unexpected greeting for the girl. Instead of menacing doom as it had done with her father, it was surprisingly pleasant. In the beginning, Beauty was frightened of the Beast, and shuddered at the sight of it. Then she found that, in spite of the monster's awful head, her horror of it was gradually fading as time went by. She had one of the finest rooms in the Castle, and sat for hours, embroidering in front of the fire. And the Beast would sit, for hours on end, only a short distance away, silently gazing at her. Then it started to say a few kind words, till in the end, Beauty was amazed to discover that she was actually enjoying its conversation. The days passed, and Beauty and the Beast became good friends. Then one day, the Beast asked the girl to be his wife. Taken by surprise, Beauty did not know what to say. Marry such an ugly monster? She would rather die! But she did not want to hurt the feelings of one who, after all, had been kind to her. And she remembered too that she owed it her own life as well as her father's. "I really can't say yes," she began shakily. "I'd so much like to..." The Beast interrupted her with an abrupt gesture. "I quite understand! And I'm not offended by your refusal!" Life went on as usual, and nothing further was said. One day, the Beast presented Beauty with a magnificent magic mirror. When Beauty peeped into it, she could see her family, far away. "You won't feel so lonely now," were the words that accompanied the gift. Beauty stared for hours at her distant family. Then she began to feel worried. One day, the Beast found her weeping beside the magic mirror. "What's wrong?" he asked, kindly as always. "My father is gravely ill and close to dying! Oh, how I wish I could see him again, before it's too late!" But the Beast only shook its head. "No! You will never leave this castle!" And off it stalked in a rage. However, a little later, it returned and spoke solemnly to the girl. "If you swear that you will return here in seven days time, I'll let you go and visit your father!" Beauty threw herself at the Beast's feet in delight. "I swear! I swear I will! How kind you are! You've made a loving daughter so happy!" In reality, the merchant had fallen ill from a broken heart at knowing his daughter was being kept prisoner. When he embraced her again, he was soon on the road to recovery. Beauty stayed beside him for hours on end, describing her life at the Castle, and explaining that the Beast was really good and kind. The days flashed past, and at last the merchant was able to leave his bed. He was completely well again. Beauty was happy at last. However, she had failed to notice that seven days had gone by. Then one night she woke from a terrible nightmare. She had dreamt that the Beast was dying and calling for her, twisting in agony. "Come back! Come back to me!" it was pleading. The solemn promise she had made drove her to leave home immediately. "Hurry! Hurry, good horse!" she said, whipping her steed onwards towards the castle, afraid that she might arrive too late. She rushed up the stairs, calling, but there was no reply. Her heart in her mouth, Beauty ran into the garden and there crouched the Beast, its eyes shut, as though dead. Beauty threw herself at it and hugged it tightly. "Don't die! Don't die! I'll marry you . . ." At these words, a miracle took place. The Beast's ugly snout turned magically into the face of a handsome young man. "How I've been longing for this moment!" he said. "I was suffering in silence, and couldn't tell my frightful secret. An evil witch turned me into a monster and only the love of a maiden willing to accept me as I was, could transform me back into my real self. My dearest! I'll be so happy if you'll marry me." The wedding took place shortly after and, from that day on, the young Prince would have nothing but roses in his gardens. And that's why, to this day, the castle is known as the Castle of the Rose. Diposting oleh aulia noviyanti bandar lampung 2/20/2012 08:46:00 PM
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Minggu, 19 Februari 2012 Kimia Analitik Kimia adalah ilmu yang mempelajari komposisi, struktur, dan sifat zat atau materi dari skala atom hingga molekul serta perubahan atau transformasi serta interaksi mereka untuk membentuk materi. Salah satu cabang ilmu kimia adalah kimia analitik yang merupakan analisis cuplikan bahan untuk memperoleh pemahaman tentang susunan kimi dan strukturnya. Kimia analitik dibagi menjadi dua jenis yaitu:
A. Analitik kualitatif Analisis kualitatif adalah analisa yang dilaksanakan untuk mengetahui jenis zat atau komponen yang terkandung dalam suatu sampel.Artinya analisa ini hanya dapat menentukan jenis bahan yang dikandung oleh suatu zat sampel saja. Analisis kualitatif menggunakan 2 macam uji : 1. Uji reaksi kering : Diterapkan untuk zat-zat padat dan dilakukan dalam keadaan kering yaitu tanpa melarutkan sampel 2. Uji reaksi basah Untuk zat – zat dalam larutan dimana suatu reaksi berlangsung ditandai dengan terbentuknya endapan,pembebasan gas, perubahan warna B. Analitik kuantitatif Analisa kuantitatif adalah analisa kimia yang digunakan untuk menentukan jumlah (kadar ) suatu bahan yang terkandung dalam zat sampel. Contoh penentuan kadar garam dalam air laut. dengan cara kristalisasi. artinya dalam analisa ini dapat diketahui kadar bahan yang terkandung dalam zat sampel. 2 cara yang sering digunakan dalam analisa kuantitatif: Gravimetri Gravimetri adalah proses isolas (pemisahan) yang berkaitan dengan gravitasi. Analisis gravimetri adalah salah satu metode analisis kuantitatif suatu zat atau komponen melalui proses isolasi dan pengukuran berat suatu unsur atau senyawa tertentu dalam keadaan murni. 2 metode yang sering digunakan untuk menghitung kadae suatu analit dalam analisis grvimetri: 1. gravimetri pengendapan =>> Penentuan suatu cuplikan secara gravimetri mula-
mula ditimbang, dilarutkan dalam pelarut tertentu kemudian diendapkan kembali dengan reagen tertentu. Senyawa yang dihasilkan harus memenuhi sarat yaitu: memiliki kelarutan sangat kecil sehingga bisa mengendap kembali dan dapat dianalisis dengan cara menimbang. Endapan yang terbentuk dikeringkan pada suhu 100-130 derajat celcius atau dipijarkan sampai suhu 800 derajat celcius tergantung suhu dekomposisi dari analit. Pengendapan kation misalnya, pengendapan sebagai garam sulfida (misalnya Cu2 S, ZnS), pengendapan nikel dengan DMG, pengendapan perak dengan klorida atau logam hidroksida (misalnya Ca(OH)2 , NaOH,dll ) dengan mengatur pH larutan. Penambahan reagen dilakukan secara berlebihan untuk memperkecil kelarutan produk yang diinginkan. aA +rR ———-> AaRr(s) Penambahan reagen R secara berlebihan akan memaksimalkan produk AaRr yang terbentuk. 2. grvimetri penguapan =>> Metode penguapan dalam analisis gravimetri digunakan
untuk menetapkan komponen-komponen dari suatu senyawa yang relatif mudah menguap. Cara yang dilakukan dalam metode ini dapat dilakukan dengan cara pemanasan dalam gas tertentu atau penambahan suatu pereaksi tertentu sehingga komponen yang tidak diinginkan mudah menguap atau penambahan suatu pereaksi tertentu sehingga komponen yang diinginkan tidak mudah menguap.Metode penguapan ini dapat digunakan untuk menentukan kadar air(hidrat) dalam suatu senyawa atau kadar air dalam suatu sampel basah. Berat sampel sebelum dipanaskan merupakan berat senyawa dan berat air kristal yang menguap. Pemanasan untuk menguapkan air kristal adalah 110-130 derajat celcius, garam-garam anorganik banyak yang bersifat higroskopis sehingga dapat ditentukan kadar hidrat/air kristal. Titrimetri Analisa titrimetri adalah analisis kuantitatif dengan mereaksikan suatu zat yang dianalisis dengan larutan baku (standar) yang telah diketahui konsentrasinya secara teliti, dan reaksi antara zat yang dianalisis dan larutan standar tersebut berlangsung secara kuantitatif. 1. Indikator adalah zat yang ditambahkan untuk menunjukkan titik akhir titrasi
telah di capai. Titik Ekuivalen adalah titik dimana terjadi kesetaraan reaksi secara stokiometri antara zat yang dianalisis dan larutan standar. Titik akhir titrasi adalah titik dimana terjadi perubahan warna pada indicator yang menunjukkan titik ekuivalen reaksi antara zat yyang dianalisis dan larutan standar. Pada umumnya, titik ekuivalen lebih dahulu dicapai lalu diteruskan dengan titik akhir titrasi. Ketelitian dalam penentuan titik akhir titrasi sangat mempengaruhi hasil analisis pada suatu senyawa. Syarat-syarat yang harus dipenuhi untuk dapat dilakukan analisis volumetric adalah sebagai berikut : 1. Reaksinya harus berlangsung sangat cepat. 2. Reaksinya harus sederhana serta dapat dinyatakan dengan persamaan reaksi yang kuantitatif/stokiometrik. 3. Harus ada perubahan yang terlihat pada saat titik ekuivalen tercapai, baik secara kimia maupun secara fisika. 4. Harus ada indicator jika reaksi tidak menunjukkan perubahan kimia atau fisika. Indikator potensiometrik dapat pula digunakan. Alat-alat yang digunakan pada analisa titrimetri ini adalah sebagai berikut : 1. Alat pengukur volume kuantitatif seperti buret, labu tentukur, dan pipet volume yang telah di kalibrasi. 2. Larutan standar yang telah diketahui konsentrasinya secara teliti atau baku primer dan sekunder dengan kemurnian tinggi. 3. Indikator atau alat lain yang dapat menunjukkan titik akhir titrasi telah di capai. Penggolongan analisis titrimetri ini, berdasarkan ; 1. Reaksi Kimia : · Reaksi asam-basa (reaksi netralisasi) · Reaksi oksidasi-reduksi (redoks) · Reaksi Pengendapan (presipitasi) · Reaksi pembentukan kompleks 2. Berdasarkan cara titrasi · Titrasi langsung · Titrasi kembali (titrasi balik/residual titration) 3. Berdasarkan jumlah sampel · Titrasi makro : Jumlah sampel : 100 – 1000 mg Volume titran : 10 – 20 mL Ketelitian buret : 0,02 mL. · Titrasi semi mikro : Jumlah sampel : 10 – 100 mg Volume titran : 1 – 10 mL Ketelitian buret : 0,001 mL · Titrasi mikro : Jumlah sampel : 1 – 10 mg Volume titran : 0,1 – 1 mL Ketelitian buret : 0,001 mL
Diposting oleh aulia noviyanti bandar lampung 2/19/2012 10:43:00 AM
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Tahapan Analisis Kimia 1. Tahapan untuk Analisis Kuantitatif • Sampling • Preparasi Sampel • Pengukuran • Perhitungan dan Interpretasi data 2. Kesalahan dalam Analisis Kimia a. Kesalahan tak tentu/ Indeterminat Error Sumber penyebab Kesalahan tak dapat ditentukan secara pasti. Contoh: - Kebisingan & penyimpangan dalam rangkaian elektronika - Getaran dalam suatu gedung - Perubahan kondisi lingkungan kerja b. Kesalahan tertentu/ Determinant Error/ Kesalahan sistematik - Kesalahan Metode/ Cara Analisis : Umumnya bersumber dari adanya zat lain yang mempengaruhi hasil pengukuran. Hasil pengukuran bisa menjadi lebih besar atau lebih kecil dari yang seharusnya - Kesalahan Operasional: Umumnya terjadi karena keterbatasan kemampuan analis/operator - Kesalahan Instrumental: Ketidakmampuan alat ukur untuk bekerja sesuai standar yang diperlukan BAHAYA DIDALAM LABORATORIUM Bahaya Bersifat Fisik Listrik Terpeleset, tersandung dan jatuh Temperatur ekstrem (panas dan dingin) Ventilasi yang buruk Tingkat pencahayaan yang kurang Radiasi Getaran mekanis Kekurangan oksigen Terkena benda jatuh (contoh: tertimpa silinder gas) Kelembaban udara Benda tajam Bahaya Bersifat Kimia Bahaya kimia berhubungan dengan penyimpanan, penanganan dan pemakaian bahan kimia berbahaya atau B3 di laboratorium. Bahayanya meliputi terciprat, tumpah, tertelan, terhirup, terhisap, kontak dengan kulit, kontak dengan mata dan lain-lain. Daftar bahaya di atas masih bisa dikembangkan, sesuai dengan kondisi masing-masing laboratorium di perusahaan. Untuk mempermudah melakukan identifikasi bahaya, lakukan dengan cara inspeksi langsung atau field inspection LAMBANG BAHAYA BAHAN KIMIA BERBAHAYA
Diposting oleh aulia noviyanti bandar lampung 2/19/2012 10:37:00 AM
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