外文翻譯----脂肪中甘油組分的測定分析

1、<p>　　畢業(yè)設(shè)計(論文)外文資料翻譯</p><p>　　題 目: </p><p>　　院系名稱： 專業(yè)班級： </p><p>　　學(xué)生姓名： 學(xué) 號： </p>

2、<p>　　指導(dǎo)教師： 教師職稱： </p><p>　　起止日期： 地 點: </p><p>　　附 件： 1.外文資料翻譯譯文；2.外文原文。 </p><p>　　附件1：外文資料翻譯譯文</p><p>　　脂肪中甘油

3、組分的測定分析</p><p>　　By A.F.NELSON, P.DeCOURCY, H.MATTHEWS and C.J.ROBERTSON</p><p>　　LEVER BROTHERS COMPANY,CMABRIDGE,MASS.</p><p>　　甘油可以從皂化脂肪中提取，如何精確快速測出甘油對肥皂及其同類行業(yè)來說相當(dāng)重要。近年來，一些有關(guān)快速皂化

4、和甘油測定委員會的活動證明了這一點。</p><p>　　常見的從脂肪中提取甘油的方法分為三個部分：皂化、氧化、滴定或測定朝氧化劑。每部分操作都有幾種不同的方法，鑒于它們之間細(xì)微的差別，整個操作過程可以有無數(shù)個方案。這篇論文的目的就是簡要將這方面的方法介紹一下：Ⅰ、直接皂化 ，Ⅱ、A.O.C.S.委員會提供的甘油測定法，Ⅲ、卡芮士試管法，Ⅳ、催化法，用硬脂酸或膨土作催化劑，最后比較分析的結(jié)果和所用的時間。<

5、/p><p><b>　?、?、直接皂化</b></p><p>　　這種方法適用于含自由脂肪酸較高的脂肪，需要一個加過50％氫氧化鉀溶液和蒸餾水的重約4克的樣本，還要把這種混合物回流85分鐘。加入熱水后，放入蒸汽槽中過夜。第二天早上混合物變成了可以裝滿一個300㏄燒杯的酸性液體，脂肪酸被除去了。用硫酸鋁和氫氧化鈉凈化溶液，再用iodiometric法測定甘油。向整數(shù)值得那

6、部分中加入重鉻酸鉀溶液和濃硫酸，加熱15分鐘后冷卻。加入碘化鉀溶液，釋放出的碘用純硫代硫酸鈉滴定，用淀粉作指示劑。這種方法盡管對含自由脂肪蘇較高的脂肪有著令人滿意的效果，但對含自由脂肪酸較低的脂肪卻達(dá)不到這種效果，在后者中皂化不能徹底進(jìn)行。</p><p>　?、?、A.O.C.S.委員會提供的甘油測定法</p><p>　　A.O.C.S.所屬的甘油分析委員會最近提出了一種皂化方案。融有5

7、克脂肪酸和5㏄濃度為50％的氫氧化鉀的溶液每隔15分鐘加熱一次，分四次進(jìn)行，溫度控制在105℃。每次加熱后都要充分?jǐn)嚢枰淮?。用重鉻酸碘作氧化劑，多余的部分用硫酸亞鐵銨滴定，氰化碘作表面指示劑。</p><p>　　A.O.C.S.采用的精練椰子油、棉籽油、氫化棉籽油和動物油等樣本，都是優(yōu)質(zhì)的，通過上述方式皂化。氧化和滴定的采用：⑴、⑵委員會提供的。結(jié)果列在表Ⅰ中。</p><p>　　我們

8、注意到在前面四個試驗中，除了棉籽油和氫化棉籽油的皂化顯然是不徹底的。從皂化值和酸值來看結(jié)果和理論數(shù)據(jù)是一致的。結(jié)果中平均值得偏差在椰子油和動物油是正的，而在棉籽油和氫化棉籽油卻是負(fù)的，除了氫化棉籽油，其它油采用第一種方法測定甘油時出現(xiàn)的偏差比采用第二種方法時大。</p><p>　　這種方法對椰子油和動物油很適用，但卻不適用于棉籽油和氫化棉籽油，因為前四個試驗在表1中顯示的皂化結(jié)果是不徹底的。試驗5和6是由一個不

9、熟悉這種方法的化驗員作的。關(guān)于這兩種有的分析結(jié)果都是很低，這和事實很吻合。當(dāng)椰子油、棕櫚油和蓖麻油情誼地皂化時，動物油和氫化油等油類卻皂化很慢。皂化的容易度和不飽和甘油脂的分?jǐn)?shù)成反比。動物油被列入易皂化行列而棉籽油和氫化棉籽油屬于不易皂化油類的事實證明這種方法是一種改進(jìn)。我們相信這種方法是成功的，而它的成功原因在于機(jī)械的攪拌引起的充分混合。攪拌釋放出的油粒子被最初反應(yīng)形成的香皂錮囚，乳膠在105℃的烤箱中非常穩(wěn)定，而皂化就是在烤箱中進(jìn)行

10、的。再次加入少量的氫化鉀，如過量的話，肥皂在產(chǎn)生時會鹽析，從而導(dǎo)致油脂中乳化劑和腐蝕劑無效。</p><p><b>　　Ⅲ、卡芮士試管法</b></p><p>　　我們實驗室建議讓皂化在試管中進(jìn)行。這種方法是把5克脂肪或油脂放進(jìn)卡芮士試管，加入50％的氫氧化鉀溶液(動物油和棕櫚油3㏄；椰子油4㏄)，把試管放進(jìn)蒸汽槽中，從而溶化那些在注入時沾在試管壁上的油脂，加入2

11、5㏄的蒸餾水使其從試管壁上流下，然后密封并冷卻試管，充分振蕩，并在130℃-135℃的卡芮士烤箱中加熱一夜，用重鉻酸鉀氧化；過量的用硫代硫酸鈉滴定，有淀粉作指示劑。這種方法得到的結(jié)果和第一方法得到的結(jié)果及用脂值測定的結(jié)果都列在表Ⅱ中。</p><p>　　我們看到前四個試驗的結(jié)果和第一種方法和卡瑞士試管得出的結(jié)果是一致的。但兩者都在用脂標(biāo)準(zhǔn)測出的甘油含量上有所不同，這些不同酸化油比不純油要大些。這和實驗室的試驗很

12、吻合。第一種方法對精練動物油類并不適用，但我們注意到在這些試驗中卡芮士試管法測出的結(jié)果和用脂標(biāo)準(zhǔn)算出的結(jié)果是一致的。</p><p>　　這項工程延伸到了精練油和純油的范圍，結(jié)果列在表Ⅲ中。</p><p>　　這組試驗做完后我們發(fā)現(xiàn)椰子油比其它油需要的溫度都低，仔細(xì)研究溫度的作用很可能會發(fā)現(xiàn)完全皂化所需要的條件。</p><p>　　棉籽油、氫化棉籽油和動物油的測

13、定平均值分別是+0.24％、+0.27％、+0.17％，這些數(shù)據(jù)都是從皂化值和酸值中得出來的。而理論數(shù)據(jù)中最大的測定偏差分別是+0.79％、+0.50％、+0.36％，這些偏差比預(yù)想的要大。通過改進(jìn)氧化合滴定可能會得到更精確地數(shù)據(jù)。</p><p>　　在長時間的加熱過程中氫氧化鉀不斷地碰撞卡芮士試管壁，為使肥皂變成脂肪酸硫酸過量，同時硅酸沉淀。</p><p>　　當(dāng)過量的硫酸何氫氧化鉀

14、中時硅就消失了，同時很可能創(chuàng)造高紀(jì)錄?？ㄜ鞘吭嚬軆?nèi)壁上殘留物的形狀會引起大家的疑問：什么時候肥皂會成為膠體，甘油會分離出來？為此我們似乎有必要深入研究一下這種方法。</p><p><b>　　Ⅳ、催化法</b></p><p>　　把α-苯酚、β-苯酚和麝香草酚作為皂化的催化劑，這已經(jīng)被描述和增加的效率示范。膨土很可能是最活躍和常見的催化劑。在這種情況下一種催化劑的

15、適用實際上是建議實驗室在皂化時用乳化劑。</p><p><b>　　硬脂酸</b></p><p>　　在含自由脂肪酸的油類易皂化的基礎(chǔ)上，加入少量硬脂酸可以精煉和凈化將要皂化和測定甘油含量的脂肪，而且那些第一種方法不能皂化的油類會很容易被皂化。達(dá)到令人滿意的效果所需條件和硬脂酸及50％的氫氧化鉀的量回有所不同。這些穩(wěn)定的棉子油類被稱為A類油脂。</p>

16、<p>　　氫氧化鉀的量首先呈現(xiàn)出從4㏄到8㏄的遞進(jìn)，以此來判斷那個量會產(chǎn)生最好的乳化劑，數(shù)據(jù)列在表Ⅳ中。</p><p>　　在此基礎(chǔ)上和類似的試驗證明，把4㏄50％的氫氧化鉀溶液定為標(biāo)準(zhǔn)。</p><p>　　由經(jīng)驗我們知道，對于A類脂肪酸，當(dāng)氫氧化鉀加入加熱到140℃-150℃的油脂中時最好的乳化劑就會產(chǎn)生。</p><p>　　為了查明溫度產(chǎn)生

17、的確切影響，我們又做了一系列試驗。在這些試驗中每個試驗的溫度都被提升了10℃，第一個實驗的溫度是100℃。觀察得到的結(jié)果列在表Ⅴ中。</p><p>　　早前的試驗被確切的證實了，140℃-150℃是向油脂中加入氫氧化鉀的標(biāo)準(zhǔn)溫度。一個皂化試驗采用了最初的溫度160℃-170℃，測出的甘油比率為10.26％，這與皂化和酸值計算出的10.68％相差甚遠(yuǎn)。換句話說就是粒狀的乳化劑不可能引起完全皂化。</p>

18、;<p>　　研究發(fā)現(xiàn)另一個因素是產(chǎn)生好的乳化劑的硬脂酸的量。它的范圍是占A類油脂重量的0-64％，每次以0.8％遞增。以此產(chǎn)生的乳化劑列在表Ⅵ中。</p><p>　　觀察發(fā)現(xiàn)4％的量可以產(chǎn)生及好的較大量的乳化劑，所以這個量就被視為標(biāo)準(zhǔn)。</p><p>　　這些條件具備之后還要討論時間問題。在所作的一系列試驗中，每個開始的時間都比前一個晚5分鐘，第一個被放在溫度控制在10

19、5℃的烤箱中25分鐘。結(jié)果顯示在表Ⅶ中，同時還有另一組的時限20分鐘的結(jié)果。</p><p>　　從這些數(shù)據(jù)來看， 20分鐘時限是完全皂化的最佳時間。</p><p>　　最初這種加熱是在一個熱盤上進(jìn)行的。這符合直接皂化法，但是通過觀察發(fā)現(xiàn)高溫破壞了乳化劑，并且盡管持續(xù)加熱并搖動的兩個小時皂化還是不徹底。確定了皂化的最佳條件，用硬脂酸作催化劑，我們的注意力放到了Silman的α-苯酚和膨土

20、上。</p><p><b>　　α-苯酚</b></p><p>　　盡管α-苯酚很可能是快速造化的極佳催化劑，但它不使用于甘油測定的分析，因為它顯然被重鉻酸鉀氧化了，那明顯比由支標(biāo)準(zhǔn)算出的甘油百分率高出許多。當(dāng)空白用完，沒有脂肪和使用于明顯的人訂正的百分比， 所得結(jié)果比較低。α-苯酚易溶于脂肪酸而不溶于水，這和事實是一致的。即使不是這樣，用α-苯酚作催化劑的效率仍

21、低于硬脂酸，因為它包含了空白測定。</p><p><b>　　膨土</b></p><p>　　膨土的效果也令人滿意。它沒有像Silman建議的那樣鉀溶液加入到腐蝕性溶液中去，而是在放腐蝕性物之前加入融化的脂肪酸中去。它生產(chǎn)一種好的乳化劑，并且結(jié)果可以和使用了硬脂酸的測定相比。</p><p>　　可能它不是膨土中純的硬脂酸催化劑引起的渾濁，

22、而且也不可能憑肉眼觀察來判斷皂化或是否完全生成皂液。</p><p>　　重量約脂肪酸5％的膨土作為標(biāo)準(zhǔn)。在105℃的烘箱中進(jìn)行皂化所用的時間通過兩組有關(guān)從A類油脂中獲取甘油的測定試驗查明了，這和制造硬脂酸很相似。結(jié)果列在表Ⅷ中。</p><p>　　20分鐘再次被選定為皂化所需的合理時長。</p><p>　　催化劑、硬脂酸和膨土隨即被運用到高度凈化油類的皂化中。

23、研究發(fā)現(xiàn)相對于最初加入催化劑時的那些油類的溫度，140-150對椰子油和動物油來說太高了，并且也產(chǎn)生了不好的乳化劑。110-120算高了，與動物油和椰子油相比，對氫化棉子油和棉子油的量也大了。作為催化劑的硬脂酸和膨土的數(shù)據(jù)列在表Ⅸ中。</p><p>　　從這兩種催化劑中得出的值非常一致，而且也與皂化值和酸值算出來的結(jié)果吻合。</p><p>　　我們必須加大對水溶液凈化的關(guān)注，水溶液含有

24、椰子油中的甘油。因為的它明顯的含有可以看到的非甘油類氧化物，如不將它除去會使重鉻酸鉀持續(xù)不斷的減少，進(jìn)而影響高濃度甘油的產(chǎn)生。</p><p><b>　　結(jié)論</b></p><p>　　通過各種途徑得出的結(jié)論的概述列在表Ⅹ中。</p><p>　　硫代硫酸鹽委員會給出的結(jié)果是通過委員會提出的皂化試驗得出的，甘油的測定是通過硫代硫酸鹽法作的。

25、后者比前者與理論更吻合。</p><p>　　有關(guān)這些結(jié)果調(diào)查顯示，這些方法在精確方面不分伯仲，很可能在很多情況下把多樣化歸因于方法的有限的不足之處。通過卡芮士得出的結(jié)果比其它方法高些，這些或許是也或許不是重要。</p><p>　　不管硬脂酸還是膨土，使用催化劑簡單快速的方法顯然是和其它討論過方法一樣可靠。硬脂酸使用可以讓我們在油脂皂化后得到一種澄清的溶液，而膨土不可以。膨土的優(yōu)勢在于最

26、初溫度要求不低于100℃的油脂，可以在同一個105℃的烘箱中加熱并完成皂化，而不是把細(xì)口瓶放在160℃的蒸汽浴中加熱。如果沒有105℃的烘箱，加熱可以在最初和皂化過程中通過細(xì)口瓶的一部分進(jìn)入沸水中來完成。</p><p>　　催化劑法皂化的優(yōu)勢在于所需的時間縮短了，這種方法只需20分鐘，相比之下委員會提供的方法則需1.5個小時，而卡芮士發(fā)則要1夜。</p><p>　　從表Ⅹ給出的結(jié)果來看

27、，脂肪酸中的甘油百分率可能取決于催化劑法皂化和重鉻酸鉀及硫代硫酸鈉法的氧化和滴定。不過運用催化劑法用重鉻酸鉀氧化，用硫酸亞鐵銨滴定在皂化時適當(dāng)?shù)难娱L一點時間，就有可能得到根高的精確度。跟多的工作已經(jīng)開展，那就是研究二苯胺作為指示劑在用硫酸亞鐵滴定過量的重鉻酸鉀時的作用，和電位滴定在這個分析中使用性的測定。這兩種方法都有希望成功，都有可能提高精確度，縮短時長。</p><p><b>　　催化劑法的步驟&

28、lt;/b></p><p>　　用一只100㏄的萃取細(xì)口瓶在分析天平上精確的稱出4±0.1克的脂肪酸樣本，用帶刻度的滴管加入約0.16克的硬脂酸或0.20-0.60克的膨土(動物油和椰子油0.20克，氫化棉子油0.40，棉籽油0.60克)。把加入的硬脂酸的氫化棉子油和棉子油加熱到140℃-150℃，把動物油和椰子油放入160℃-165℃的油浴中3分鐘加熱到110℃-120℃。如果使用的是膨土先把

29、脂肪在水浴中或105℃的烘箱中加熱到100℃，轉(zhuǎn)動并振蕩細(xì)口瓶是催化劑均勻地在分布脂肪中，然后緩慢地加入4㏄50％的氫氧化鉀溶液，并用力振蕩混合，使其持續(xù)轉(zhuǎn)動30秒，然后放入105℃的烘箱中，20分鐘后肥皂被液化，溶液清澈了，氧化完成且多余的氧化物被滴定。</p><p><b>　　總結(jié)</b></p><p>　　準(zhǔn)備好幾種皂化脂肪易便進(jìn)行甘油測定的方法被采納。&

30、lt;/p><p>　?、瘛⒅苯釉砘?，Ⅱ、A.O.C.S.委員會提供的甘油測定法，Ⅲ、卡芮士試管法，Ⅳ、快速造化法。為試驗提供的從油脂中測定甘油產(chǎn)量的方法，必須用硬脂酸或膨土作催化劑。在加入氫氧化鉀和用力振蕩后，理想的乳化劑為皂化提供了必須的條件。皂化在烘箱中進(jìn)行，20分鐘后完成。</p><p>　　提議的方法有以下優(yōu)勢：Ⅰ、皂化在20分鐘內(nèi)完成，Ⅱ不需要特定儀器，Ⅲ、皂化在較低的溫度(1

31、10℃-120℃)下進(jìn)行，Ⅳ、方法簡單沒有特別技術(shù)要求，Ⅴ、結(jié)果和理論數(shù)據(jù)及其它方法得到的結(jié)果一致。</p><p><b>　　附件2：外文原文</b></p><p>　　SOME NOTES </p><p>　　ON THE DETERMINATION OF GLYCEROL IN FATS</p><p>　　

32、By A. F. NELSON, P. DeCOURCY, H. MATTHEWS, and C. J. ROBERTSON.</p><p>　　LEVER BROTHERS COMPANY, CAMBRIDGE, MASS.</p><p>　　The accurate and rapid determination of glycerol that can be produced b

33、y saponifying fats is of great importance to the soap and allied industries. That it is still a great vital problem is indicated by the recent articles regarding rapid saponification 1,2 and rapid determination of glycer

34、ol 8, and the activity of the Committee on Glycerol Determination.</p><p>　　The usual method of analysis of fats for available glycerol divides itself into three operations: saponificationl oxidation, and ti

35、tration or determination of excess oxidant. Each of these operations may be performed in a number of different ways, and considering the many slight variations in the various procedures an almost innumerable number of wa

36、ys of performing the entire analysis are available. It is the purpose of this paper to consider briefly, first, a few of the methods</p><p>　　I. The d i r e c t saponification method.</p><p>　　I

37、I. The method proposed by the A. O. C. S. Committee on Glycerol Determination.</p><p>　　III. The method involving the use of a Carius tube; also to propose and discuss a new method.</p><p>　　IV.

38、 The catalytic method, using stearic acid or bentonite as catalysts, and, finally, to compare the results of the analyses and the time involved.</p><p>　　I. The Direct Saponification Method</p><p&

39、gt;　　This method, used for fats relatively high in free fatty acids, calls for a 4-gram sample of fat to which is added 50% aqueous potassium hydroxide and distilled water, and the mixture refluxed for 5/4hours. After ad

40、dition of hot water, it is placed on the steam bath overnight.In the morning, the solution is transferred quantitatively to a 300 cc. beaker and acidified, and the fatty acids removed. The solution is cleared with alumin

41、um sulphate and sodium hydroxide, and the glycerol determined by </p><p>　　solution and concentrated sulphuric acid. This solution is then boiled for 15 minutes and cooled. Potassium iodide solution is added

42、 and the liberated iodine is titrated with standard sodium thiosulphate solution, using starch as the indicator. This method, although it works satisfactorily for fats relatively high in free fatty acids, is entirely uns

43、atisfactory for fats low in free fatty acids, in that the saponification is incomplete.</p><p>　　Ⅱ. The Method Proposed bythe A. O.C. S. Committee</p><p>　　The Glycerine Analysis Committee of th

44、e A. O. C. S. recently proposed for cooperative work a method of saponification in which 5 grams of the melted fat are mixed with 5 cc. of 50% aqueous potassium hydroxide and heated to 105 ° C. for four 15-minute pe

45、riods. At the end of each period, thorough mixing of the fat and the potassium hydroxide is essential. Potassium dichromate is used as the oxidizing agent, the excess titrated with ferrous ammonium sulphate solution,usin

46、g potassium ferricyanideas </p><p>　　A. O. C. S. samples of refined coconut oil, cottonseed oil, hydrogenated cottonseed oil, and tallow, all high-grade, were saponified by this method and the oxidation and&

47、lt;/p><p>　　titration operations were done by two methods, (1) the iodiometric method for glycerol in soap and (2) that described by the committee.The results are given in Table I.</p><p>　　It will

48、 be noted that in all cases of the first four experiments, except in one case for cottonseed oil and one for hydrogenated cottonseed oil, in which saponification is</p><p>　　obviously incomplete, the results

49、 are in fairly good agreement with the theoretical values, calculated from the saponification and acid values. The deviation of the average of the results from these is positive for coconut and tallow and negative for<

50、;/p><p>　　.cottonseed oil and hydrogenated cottonseed oil. Except for hydrogenated cottonseed oil, the deviations are greater when the glycerol is determined by method (1) than by method (2).</p><p&g

51、t;　　While this method is very satisfactory for coconut oil and for tallow, it is not entirely reliable for cottonseed oil and hydrogenated cottonseed oil, as in one case of the first four for each of these oils given in

52、Table I saponification was incomplete.</p><p>　　In Experiments No. 5 and No. 6, performed by an analyst unfamiliar with the method, both results for these two oils were low. This is in agreement with the fac

53、t that while coconut oil, palm kernel oil, and castor oil will saponify quite easily, tallow and hydrogenated oils, etc., saponify much more slowly; and that the ease of saponification is inversely proportional to the fr

54、action of unsaturated glycerides present. That the nlethod is an improvement is shown by the fact that tallow is here inc</p><p>　　Again the excess potassium hydroxide is small. With greater excess there is

55、a tendency for the soap when formed to salt out, thereby causing the emulsion of the oil and aqueous caustic solution to break down.</p><p>　　III. The Method Involving the Use of a Carius Tube</p><

56、;p>　　The idea was suggested in our laboratory that the saponification operation be made in a Carius tube. In this method, 5 grams of fat or oil is placed in a Carius tube, 50%</p><p>　　potassium hydroxide

57、 solution added (3 cc. for tallows and palm oils and 4 cc. for coconut oils), and the Carius tube heated in a steam bath to melt any oil which may have spattered on the wall of the tube when it was introduced. Twentyfive

58、 cc. of distilled water are added, washing down the walls of the tube, which is then sealed and annealed, thoroughly shaken and heated overnight in the Carius oven at 130-135 ° C. The oxidation is done by means of p

59、otassium dichromate, the excess of which is ti</p><p>　　Results by this method compared with those of Method I as well as those determined from the ester values are given in Table II.</p><p>　　I

60、t will be seen that in the first four cases the results of Method I and the Carius Method agree very well, but both vary from the percentage glycerol determined from the ester value. The variation is greater for the acid

61、ulated oils than for the unrefined oils, a fact which is in agreement with laboratory experience. Method I is not applicable to such oils as refined tallow, but it will be noted in these cases that the results of the Car

62、ius Method agree very well with those calculated from the e</p><p>　　This work was extended to the refined and pure oils, the results of which are given in Table III.</p><p>　　After this set of

63、experiments was completed it was found that coconut oil requires a lower temperature than the other oils, and probably if the effect of temperature were studied, a condition for complete saponification could be ascertain

64、ed.</p><p>　　The averages of several determinations for Cottonseed oil, hydrogenated cottonseed oil, and tallow vary +0.24, +0.27, and -+0.17 percent, respectively, from the calculated values obtained from t

65、he saponification and acid numbers, while the greatest deviation of a single determination differed from t'he theoretical value by +0.79, +0.50, and +0.36 percent, respectively. These deviations are greater than is d

66、esirable. It may be that by improved methods of oxidation and titration greater accuracy m</p><p>　　The potassium hydroxide attacks the glass of the Carius tube during the prolonged heating and when the sulp

67、huric acid is added in excess to convert the soap to fatty acids, silicic acid is precipitated. When the excess sulphuric acid is neutralized with sodium hydroxide the silica causes a fugitive end point and may possibly

68、be responsible for the high results noted. The etchings on the inside of the Carius tube are of such appearance as to raise considerable doubt as to just when all the soap j</p><p>　　IV. The Catalytic Method

69、</p><p>　　The use of cc-naphthol, fl-naphthol, and thymoP as catalysts in saponification has been described and increased efficiency demonstrated. It has been stated that bentonite 5 is probably the most act

70、ive and generally useful catalyst for this purpose.</p><p>　　The use of a catalyst, which in this case is actually an emulsifying agent was thus suggested for laboratory saponification.</p><p>　

71、　A. Stearic Acid</p><p>　　On the basis of easy saponification of oils containing free fatty acids, small quantities of steark acid were added to refined and purified fats when these were to be</p><

72、;p>　　saponified and the percentage of glycerol determined, and it was found that oils which could not be saponified by the direct method were then readily saponified. Conditions</p><p>　　and amounts of st

73、earic acid and 50% potassium hydroxide were varied to determine those most satisfactory for complete saponification of an oil of the hardened cottonseed type, which we shall designate as Oil A.</p><p>　　The

74、quantity of potassium hydroxide was first varied from 4 to 8 ㏄. to determine which gave the best emulsion. The data are given in Table IV.</p><p>　　On the basis of this and similar experiments, 4 cc. of 50%

75、aqueous potassium hydroxide was chosen as standard</p><p>　　From experience it was known that for this particular Oil A, the best emulsion resulted when the potassium hydroxide was added to the oil which was

76、 heated to a temperature of 140-150 ° C. However, to ascertain the exact influence of temperature, a series of experiments in which the temperature was increased by 10 ° C. for each member of the series over th

77、e previous member, with the first one at 100 °C., was performed. The observations made are recorded in Table V.</p><p>　　The earlier experience was definitely substantiated and 140-150 °C. was sele

78、cted as the standard temperature of the oil when the potassium hydroxide was added. A single saponification was made, with the initial temperature of the oil at 160-170 ° C., and the percentage of glycerol determine

79、d and found to be 10.26% as compared with 10.68%, calculated from the saponification and acid values. In other words, a grainy emulsion will not lead to complete saponification.</p><p>　　The next factor to b

80、e studied was that of quantity of stearic acid most efficient in producing a good emulsion. The amount was varied from 0 to 6.4% of the weight of the Oil A in increments of 0.8%. The appearance of the resulting emulsions

81、 is listed in Table VI.</p><p>　　Four per cent of stearic acid was found to produce as fine an emulsion as larger amounts, and that quantity was then standardized as the most efficient.</p><p>　

82、　After these conditions were established, the time factor was studied.A series of determinations was made, in which each one was started five minutes after the previous one, the first one being kept in the 105 °C. o

83、ven for 25 minutes. Table VII gives the results of this series as well as those of a second series in which 20 minutes was the time limit.</p><p>　　From these data it was concluded that 20 minutes was suffic

84、ient time for complete saponification.</p><p>　　Originally this heating was attempted on a hot plate in conformity with the direct saponification method, but it was observed that the high temperature destroy

85、ed the emulsion and in spite of continued heating and shaking for two hours the saponification was observed to be far from complete.</p><p>　　Having now determined the best conditions for saponification usin

86、g stearic acid as the catalyst, we turned our attention to ~-naphthol suggested by Silman and bentonite suggested by Smith.</p><p>　　B. α --Naphthol</p><p>　　Although α-naphthol may be an excell

87、ent catalyst for rapid saponification,it was found to be unsuitable for use in analysis involving the determination of glycerol, as it is apparently oxidized by the potassium dichromate solution since the apparent percen

88、tage of glycerol is considerably higher than that calculated from the ester value. When a blank was run, without the fat, and the correction applied to the apparent</p><p>　　percentage, the result was lower.

89、 This coincides with the fact that the cc-naphthol is readily soluble in the fatty acids and only slightly soluble in water. Even if this were not the case, the use of ~-naphthol as a catalyst would be more cumbersome th

90、an stearic acid since it involves a blank determination.</p><p>　　C. Bentonite</p><p>　　Bentonite, on the other hand, was found to be very satisfactory. Instead</p><p>　　of adding i

91、t to the caustic solution as suggested by Smith 5, it was added to the melted fat prior to the addition of the caustic. It forms a good emulsion and the results are</p><p>　　comparable with those of the dete

92、rmination in which stearic acid was used.</p><p>　　It is, possibly, not so neat a catalyst as stearic acid in that the suspended</p><p>　　bentonite causes the resultlng soap solution to be cloud

93、y and it is impossible by visual inspection to determine whether or not the saponification or subsequent solution of soap is complete. </p><p>　　Approximately 5% of the weight of the fat was chosen as the qu

94、antity of bentonite to be used: The length of time of saponification in the 105 ° C. oven was ascertained by two series of determinations of percentage glycerol available from Oil A, similar to those made for steari

95、c acid. The results are found in Table VIII.</p><p>　　Again 20 minutes was selected as a reasonable length of time for complete saponification. The catalysts, stearic acid and bentonite, were then applied to

96、 the</p><p>　　saponification of the highly purified oils; Coconut Oil, Tallow, Hydrogenated Cottonseed Oil, and Cottonseed Oil. It was found that a temperature of 140-150 ° C. for the initial temperatur

97、e of the oils when the caustic is added was too bigb for Coconut Oil and Tallow and that good emulsions are not formed. A temperature of 110-120 ° C. is far superior, Also larger quantities of bentonite are required

98、 for Hydrogenated Cottonseed Oil and Cottonseed Oil than for Tallow and Coconut Oil. Data for ste</p><p>　　There is exceIlent agreement between the values obtained with the two catalysts and these in turn ag

99、ree very well with those calculated from the saponification and acid values.</p><p>　　Considerable care must be exercised in the clarification of the aqueous solution containing the glycerol for Coconut Oil,

100、 as it apparently contains an appreciable quantity of non-glycerol oxidizable m at t e r, which if not removed gives increased reduction of the potassium dichromate and, therefore, high resuits for percentage glycerol.&l

101、t;/p><p>　　Conclusion</p><p>　　A recapitulation of the results obtained by the various methods is given in Table X.</p><p>　　The results given under "Committee Thiosulphate"