After the last portion of iodine that had been added was decolorized, the flask was placed aside to cool and to allow the iodoform to separate, when the contents of the flask were thrown on a filter, to separate the iodoform from the mother-liquor. The iodoform was then washed with a small quantity of cold distilled water, placed in folds of bibulous paper, and allowed to dry; it was then weighed, and found to amount to 0.850 grm. The product was of a light lemon colour, and very distinctly crystalline.
Although Bouchardat does not speak of treating the mother-liquor for a further separation of iodoform, Bell passed a stream of chlorine gas through the mother - liquor (as recommended in Filhol's process), after the addition of 5 grm. of bicarbonate of potassium and 12.5 cc. of alcohol, which resulted, not in the separation of iodoform, but in the liberation of violet vapours of iodine; upon adding to the liquid in the flasks a small quantity of solution of potash, there was an instantaneous production of a second quantity of iodoform, which was separated by filtration, washed, dried, and weighed. It amounted to 0.489 grm. The total amount of iodoform obtained by both separations was 1.339 grm., or 17.27 per cent. No attempt was made to obtain the iodine from the mother-liquor, for reasons that will be mentioned below.
Filhol's process (asdescribed above). Bell placed in a flask, arranged as in the preceding experiment, 2 grm. of iodine, 10 grm. of crystallized carbonate of sodium, 50 cc. of water, and 5 grm. of alcohol, and heated in a water-bath, between 140° and 160° F. (60° and 80° O.) till the liquid was decolorized, when he added 2 grm. more of iodine, 2 and again heated till decolorized. He then added 1 grm. of iodine, and continued heating until decolorized, never allowing the temperature to rise above 160° F. (80° C). The flask was then removed from the water-bath and allowed to cool, when a large quantity of iodoform of a deep yellow cast crystal-' lized out.
The contents of the flask were then thrown upon a filter; the iodoform was washed with a small quantity of distilled water to free it from the mother-liquor, and placed on folds of bibulous paper in a warm atmosphere to dry. The dry product weighed 0.834 grm.
The filtrate from this (the first separation) he returned to the flask, and added 10 grm. of crystallized carbonate of sodium, 0.5 grm. of alcohol heated to 160° F. (80° C), and passed a slow current of chlorine gas through the mixture, which at first assumed a brown colour, then was decolorized with a separation of- iodoform. The current of gas was then stopped, the flask removed from the water-bath, and allowed to cool.
The contents of the flask were then thrown upon a filter, washed, and allowed to dry. The precipitate before washing was very bulky and of a very light colour (almost white), due to the presence of iodate of sodium, which had separated in a non-crystalline condition. The dry product from this (the second separation) weighed 0*456 grm. He returned the filtrate from the second separation to the flask, and added 5 grm. of alcohol, 1 grm. of crystallized carbonate of sodium, heated to about 150° F. (65 1/2° C), and passed a current of chlorine gas through the mixture, which only caused a liberation of iodine vapours; whereupon he added 1 grm. of crystallized carbonate of sodium and 5 grm. of alcohol, still continuing the current of gas. No change having taken place in the appearance of the liquid, he added a small piece of soda, about 0.5 grm.; the liquid then became colourless, and a separation of iodoform took place. The current of gas was now stopped, the flask removed from 2 ▲ the water-bath, allowed to cool, and the contents thrown on a filter and washed. The dry product weighed 0.136 grm.
The amount of iodoform obtained from the three separations was 1.426 grm., or 28.5 per cent.
Filhol's process. This experiment is virtually a repetition of No. 2, with the exception of using three times the quantity. He placed in a flask a mixture of 30 grm. of crystallized carbonate of sodium, 150 cc. of water, 15 grm. of alcohol (95 per cent.), and 15 grm. of iodine, heated in a water-batfi, between 140° and 160° F. (60° and 80° C.), till decolorized, when iodoform was separated of a lemon-yellow colour, which, when filtered, washed, and dried, weighed 2.914 grm. He returned the filtrate to the Bask, added 30 grm. of crystallized carbonate of sodium, 15 grm. of alcohol, and returned the flask to the water-bath, heated to 150° F.(65 1/2°C.), and passed a current of chlorine gas through the mixture, which, instead of permanently decolorizing the solution, turned it almost colourless, and then changed it to a dark brown colour, whereupon he added 15 cc. of solution of potash (U. S. P.), and continued the current of chlorine gas. The solution became colourless, with a separation of iodoform in a brownish and apparently impure (or possibly in an amorphous) condition. Upon recrystallizing this from alcohol, the iodoform separated in bright yellow crystals.
The product, washed and dried, weighed 1.671 grm.
The filtrate from the second separa-tion was returned to the flask, 3 grm. of crystallized carbonate of sodium and 1.5 grm. of alcohol were added, the flask was placed on the water-bath heated to 150° F. (65 1/2° C), and a current of chlorine gas was passed through, which caused a third separation of iodoform, which was filtered while hot, to separate the iodoform from the iodate of sodium, which is much more soluble in the warm liquid than in cold. The iodate of sodium separated in fine needle-shaped crystals; the iodoform, when dry, weighedl 0 868 grm. The total amount of iodoform obtained from the three separations was 5*453 grm., or 36.35 per cert.
This experiment was simply a repetition of Filhol's process, as described above, with this difference, that Bell added to the deodorized alcohol used 1 part of amylic alcohol in 5 parts of alcohol; the iodoform obtained was of a 'deep yellow colour and of a very disagreeable odour, similar to that of commercial iodoform.
Cornells and Gille process. The results obtained with this were so unsatisfactory that Bell did not save the product. Although the amount of material taken for the experiment was as large as that taken for the other experiments, the yield was very small and of an inferior appearance. He found the other processes so much superior to this one that he did not think it worth while to repeat it.
Bouchardat's process. This process is generally recommended as the easiest to work by; in one respect it is, namely, you are not obliged by it to work over your filtrates for additional separations of iodoform by chlorine gas, as in Filhol's process; but it is an objectionable process for the following reasons: -
1. The bicarbonate of potassium used is more expensive than the carbonate of sodium used in Filhol's process.
2. It is a slower process than Filhol's, taking more time to complete the reactions.
3. The yield is not nearly so great as in Filhol's.
Bouchardat says nothing about treating the second filtrate for an additional separation of iodoform, which Bell found possible to do by passing a current of chlorine gas after adding an additional quantity of bicarbonate of potassium, alcohol, and a small quantity of solution of potash, which shows that it is possible to obtain more iodoform from the amount of iodine used than by following Bouchardat's own directions. But even if the second filtrate was treated with chlorine gas, the process would be more expensive than Filhol's, and the yield not so great.
Filhol's process Bell considers by far the most advantageous one to work by, for the following reasons: -
1. The yield is greater than by any other process tried.
2. It is cheaper.
3. It is a quicker process to work by.
4. The crystals obtained are much handsomer than by the other processes.
For those who wish to obtain an almost odourless iodoform (which they can easily do by using pure materials), Filhol's process is to be recommended, the product having only a faint saffronlike odour.
The object of this experiment was to find out whether the presence of amylic alcohol would cause the iodoform formed to have a disagreeable odour, in which respect it was successful, the product having a very disagreeable odour, closely resembling that of the commercial article, and when dissolved in alcohol it formed a reddish coloured solution, resembling that obtained by dissolving commercial iodoform exposed to the sunlight.
No attempt was made to recover the iodine from the mother-liquors, because the amount obtained was too small to work to advantage, also because the experiments were tried solely to find out which process would be the best, as regards quality and yield, for the dispensing pharmacist to employ in making iodoform for his own use. It would of course pay to save the mother-liquors until enough was obtained to make it an object to extract the iodine contained in them.