14 THE ANALI’S’P. A NEW PROCESS OF ESTIMATIXG GLPC ERIN I N FERMENTED LIQUIDS. BY L. EEGLER.* 1. THE process for the determination o€ glycerin in wines, as decided on by the Bsrlin Committee, has of late been improved, but there are still great sources of error, chiefly the loss of glycerin in the process of its purification by ether-alcohol. Pure glycerin is certainly soluble in a mixture of 1 volume of alcohol and 2 volumes of ether, but when other insoluble bodies are present they retain a not inconsiderable amount of glycerin, sometimes as much as 20 per cent. of the total. Repeated treatment with the ether- alcohol fails to completely remove all the glycerin, The process which I now recommend is based on the following principle :- The carbon of glycerin may be readily oxidized to carbonic acid by means of sulphuric acid and potassic dichromate. By using a Wills carbonic acid apparatus, and estimating tfhe loss in weight, we can calculate the amount of glycerin.The one flask contains the glycerin mixed with a saturated solution of potassic dichromate, the other contains, as usual, strong sulphuric acid. After the apparatus has been weighed, a little air is drawn out, which causes some of the acid to mix with the chromate. A regular evolution of carbonic acid soon sets in, but must be assisted towards the last by gently boiling. The flask containing the sulphuric acid must be kept cool. When no more gas bubbles are formed, the apparatus is cooled by partial immersion in cold water, and the remaining carbonic acid is expelled by a current of dry air.The apparatus is now reweighed, and the loss represents carbonic acid. The following equation shows the action taking place :- 3 C,H80, + 7 K,Cr207 + 28 H,SO, = 7 Kc,SO, + 14 Cr,(SO,), + 9 CO, + 40 H,O One part of glycerin therefore requires about 7.5 parts of K,Cr,07 and 10 parts of H2S0,, but an excess of each is of course used. The dichromate must be purified by re- crystallization. I n using a delicate balance 1 have a smaller apparatus made on purpose, and can then operate on -26 gramme of glycerin, but 1 also can work on -75 or 1 gramme ; if the balance is still sensitive to -01 or -005 grammes. The operation takes about one hour for every -25 gramme of glycerin. The following test analyses show the accuracy of the method. The glycerin actually weighed had a specific gravity of 1.2339 at 15°C.; and according to Lena’s tables contained 8608 per cent. of pure glycerin. Pure glycerin taken. Carbonic anhydride. Qlycerin founcl. 1.00 grammes. . . . . 1.445 grammes. . . . . 1.007 grammes. -500 ,, . . .. *725 ,, * . . . *505 j 9 *500 ,, . . , . *710 ,, . . . ,495 ,, 9 5 0 ,, . . .. .360 ,, . . . . *244 ,) *248 ,, . . ,. -3562 ,, . . .. *2483 ,, 950 ,, . . . . -3610 ,, .. .. ,2515 ,, -24s ,, . . . . -3587 ,, .. ,. 9600 f , The last three analyses were done with the aid of a delicate bttlance. 2. Estimation of glycerin in wine :- The crude glycerin obtained from 100 C.C. of wins, after evaporation with 3 C.C. milk of lime and 4 grammss of quartz, and extracting the inass with alcohol of 96 per * Zlepert.Anal, Chemie, 47, - _ITHE ANA4LYST. 15 -. - - -.- - -. -. -_ - -_ ___._ cent., is, after weighing, diluted up to a definite bu€k, and a!iquot parts are taken for the ash and the oxidation process. A white wine, containing 8.54 per cent. of alcohol and 2.07 per cent. solid matter, gave in 100 C.C. 1.4 grammes crude glycerin with -1278 ash. 25 C.C. of the glycerin diluted up to 50 c.c., yielding a 7 2 5 grammes GO, = 1.10 per cent, of glycerin. A duplicate experiment gave 1.47 crude glycerin with ~136 ash, *710 CO, = -99 per cent. glycerin; the average thus being 1 per cent., and the relation between alcohol and glycerin as 100 : 11.7. 3. Estimation of glycerin in wine after it has been purposely added. Three lots of 100 C.C. each of the same wine were mixed respectively with -125,950, -500 grammes of glycerin, and analysed as before.The results were as follows :- Crude glycerin. Ash. COS (28 C.C. from 50 c.c.) Glycerin in 100 C.C. 1155 . . .. ,1496 .. . . .so . . . . 1.115 1-75 , . .. -1400 .. , . *go .. . , 1.264 2 4 7 . . ,. ,1172 .. . . 1.07 . . . . 1.492 Allowing for the 1 per cent, of natural glycerin in the sample, we obtain -115, ,254, and ~492 per cent, of glycerin, The cthromate solution from the two last experiments was afterwards submitted to distillation, ond yielded about el6 grm. of acetic acid, derived from impurities in the crude glycerin. 4. Suppose it could be taken for certain, the process removes such bodies as sugar, tartmio, malic, citric, and tannic acids, which would interfere with the accuracy of the oxidation process, it would still be necessary to ascertain if there are other bodies in the orude glyoerin which would yield carbonio acid, From the experiments it would appear such a quantity of carbonic acid is constant.To separate any of these bodies, the diluted crude glycerin was mixed with an ammoniacal solution of lead acetate, the pre- cipitate filtered off, washed, dissolved in acetic acid, and this fluid, after heating to expel GO,, submitted to the oxidation process. A precipitate obtained from 100 C.C. of wine yielded an amount of carbonic acid equivalent to -035 grm. of glycerin. The true amount in the sample was therefore 1-00 - -035 = 0965 per cent, 5. Comparison of the old process with the oxidation process. 100 C.C. of the same wine treated by the old process gave the following weights of glycerin ;- After the first extraction -7177 including 0015 ash.,, swond ,, *1488 ?, -0123 ?, The residue weighed -3819 ,, -096 ,, The oxidation of these residues gave an amount of carbonic acid corresponding with -6300, 01295, and -1662, total -9257 grms. of glycerin, from which must be deducted *035. From these figures it will be seen the oxidation process is the best, the results obtained by the old process being too high, on account of small quantities of fatty and nitrogenous matters, and of organic acids, which cause the ash to contain potassic carbonate. The total glycerin, 09257, differs *0383 from the *965 grm. previously found, and this difference is due to loss during the drying of the glycerin after purifying with ether-alcohol.16 THE ANALYST.I have also got promising results with beer and sweet wines. 100 C.C. of Lager beer with 5.5 per cent. of extract, yielded after evaporation with 8 C.C. milk of lime and 5 grm. of quartz, q069 grm. of glycerin. The same beer mixed with *25 grm. glycerin gave ,308 grm. The quantity of recovered glycerin was therefore -308 - ,069 = a239 grm. For sweet wines I have introduced a modification based on the fact that glucose or invert-sugar are completely decomposed by boiling with strong alkaline fluids, like baryta water, and forms salts insoluble in spirits of wine. A quantity of wine as will yield about 3 grammes of solid residue is evaporated, first in a large basin, finally in a smaller one, with excess of baryta water, containing about 7.8 grammes of Ba2HO. Calcium hydrate does not answer so well, as too much of it is required, and the bulk is inconveniently increased.When no more water vapour is given off, the mass is mixed with 8 grammes of quartz, and then extracted four times in succession with 80 C.C. of alcohol of 85 per cent. The mixed alcoholic extracts are dis- tilled, and the residue is then ready for the oxidation process. If the wine contained cane-sugar, this must first be inverted by boiling with HC1. To test the accuracy of this process, I separated any barium from the fluid, by passing a current of CO, and adding a few drops of ammonia. After filtering and evaporating to a syrup, the residue, when dissolved in water, gave but a faint pre- cipitate with ammoniacal solution of lead acetate. Both filtrate and precipitate were subjected to the oxidation process. A sweet wine, with 15.17 per cent, alcohol and 15.91 per cent. extract was analysed, with the following result- 1. 20 C.C. = *320,-C02=.223 glycerin. 2. 20 c.c.+*496 added glycerin= 1.02 00, = -711 glycerin. Glycerin recovered, ~ 7 1 1 - -223 = *488. When Jirst treated with ammoniacal lead acetate, precipitates were formed, which I yielded an amount of CO, corresponding with no113 and 00146 grammes of glycerin. hope t o soon publish the results of further experiments.