Fat. The dried butter is now to be heated with ether (the ether should be made to boil by floating the dish in hot water). Several successive portions should be taken, the whole passed through a filter, the filter well washed with ether, and the filtrate evaporated to dryness and weighed.
Caseine and Ash. The residue from which the fat and water have been extracted is now to be taken, carefully weighed, then burned down to a low red heat; the residue remaining is the ash, the loss the caseine.
Butter-analysing dish.
The amount of ash, practically speaking, is the salt, but if there be any doubt as to its composition, the chlorine maybe estimated by a volumetric solution of nitrate of silver, and further examined.
The following table shows the composition of a few genuine and other butters, examined according to the same, or at least to a similar process to the one described:—
| Fat. | Ash, principally Salt. | Water. | Caseine. | Quality. | ||
| Fresh Devonshire butter. | 82·7 | 1·1 | 16·2 | 16·2 | Good. | Wanklyn. |
| Normandy butter. | 82·1 | 1·8 | 16·1 | 16·1 | ” | ” |
| Jersey butter. | 78·491 | 8·528 | 10·445 | 2·536 | ” | Angell and Hehner. |
| Normandy butter. | 82·643 | 2·915 | 9·305 | 5·137 | ” | |
| Butter from Ventnor. | 86·280 | 6·600 | 3·831 | 3·289 | Found to be adulterated with foreign fat. | ” |
| Butter from London. | 87·50 | 1·559 | 23·981 | 6·880 | Adulterated with water. | ” |
| ” | 47·119 | 2·689 | 42·358 | 7·834 | Adulterated with water, and contains an excess of curd. | ” |
6. A Method of Detecting Meat Fats in Butter. Mr Horsley, writing to the ‘Chemical News,’ September, 1874, says:—“My starting point is, that fresh butter is permanently soluble in methylated ether, sp. gr. 0·730 at the temperature of 65° Fahr. But with the view of seeing if any other substance it may contain could be precipitated from it, I took, say, 20 or 25 grains of fresh butter, placed it in a small test-tube, and poured over it one drachm of methylated ether, and on corking the tube it readily dissolved after a few minutes’ agitation. I then added 30 drops of methylated alcohol, 63° o. p., and agitated again, but nothing was precipitated. I, therefore, made another experiment with 15 grains of butter and 10 grains of prepared mutton fat, dissolved them in 1 drachm of ether first, and added 30 drops of alcohol, when in less than half an hour the fat was precipitated in a room heated to 68° Fahr. Next, in order to see the effects upon mixtures of known fats,
such as lard, beef, mutton, and tallow fats properly melted together in proportions of 60 grains of butter and 40 of fat, and stirring till cold, I found that each of them could, by a similar procedure, be precipitated in a few minutes. In one case, that of mutton, I filtered off the ethereal liquid, and collected the residue, and obtained as much as 30 per cent. of what had been used; so that there is no longer any doubt about easily detecting fatty adulterations in butter. Lastly, I would observe that crystallisation of butter, out of the ethereal solution at a lower temperature than 65°, must not be mistaken for the fats precipitated by alcohol alluded to, as the butter, besides being so much lighter, occupies the upper layer, and is different in character and easily remelted by the application of the warm hand for a minute or so.
“Further experiments have proved that half an hour suffices to effect the full precipitation of fats from the ethereal solutions by the addition of 20 drops or so of alcohol to the drachm of ether, containing not more than 25 grains of the adulterated butter; after which the tube should be agitated and its contents projected on to a small double filter, washed with a little alcohol, and the residue whilst moist scraped off, and transferred to a watch-glass to dry. In this way loss by melting and absorption into the paper is obviated.