Food Adulteration and Its Detection / With photomicrographic plates and a bibliographical appendix

by Jesse P. Battershall

(a) Alcohol.—In properly distilled liquors, a fairly approximate estimation of their alcoholic strength is effected by the specific gravity determination, which is best made by means of the special gravity bottle. In the case of spirituous liquors which contain extractive matters, it is necessary to first separate the alcohol present by the process of distillation, and then determine the density of the distillate when made up to the volume originally taken. The following table gives the percentages of alcohol by weight and by volume, and of water by volume, for specific gravities at 15°.[117]

The percentages of alcohol in the table are calculated for the temperature of 15°. The necessary correction for differences of temperature at which the determination is made is obtained by multiplying the number of degrees above or below 15°, by 0·4, and adding the product to the percentage shown by the table, when the temperature is lower than 15°, and deducting it when it is above.

Percentage of alcohol, by weight and by volume, and of water by volume, for specific gravity at 15°; water at same temperature being the unit:—

Specific Gravity.	Percentage.
	By Weight.	By Volume.
	Alc.	Alc.	Water.
1·0000	0·	0	100·
0·9985	0·80	1	99·05
0·9970	1·60	2	98·11
0·9956	2·40	3	97·17
0·9942	3·20	4	96·24
0·9928	4·00	5	95·30
0·9915	4·81	6	94·38
0·9902	5·61	7	93·45
0·9890	6·43	8	92·54
0·9878	7·24	9	91·62
0·9867	8·06	10	90·72
0·9855	8·87	11	89·80
0·9844	9·69	12	88·90
0·9833	10·51	13	88·00
0·9822	11·33	14	87·09
0·9812	12·15	15	86·19
0·9801	12·98	16	85·29
0·9791	13·80	17	84·39
0·9781	14·63	18	83·50
0·9771	15·46	19	82·60
0·9761	16·29	20	81·71
0·9751	17·12	21	80·81
0·9741	17·96	22	79·92
0·9731	18·79	23	79·09
0·9721	19·63	24	78·13
0·9711	20·47	25	77·23
0·9700	21·31	26	76·33
0·9690	22·16	27	75·43
0·9679	23·00	28	74·53
0·9668	23·85	29	73·62
0·9657	24·70	30	72·72
0·9645	25·56	31	71·80
0·9633	26·41	32	70·89
0·9620	27·27	33	69·96
0·9607	28·14	34	69·04
0·9595	29·01	35	68·12
0·9582	29·88	36	67·20
0·9568	30·75	37	66·26
0·9553	31·63	38	65·32
0·9538	32·52	39	64·37
0·9522	33·40	40	63·42
0·9506	34·30	41	62·46
0·9490	35·18	42	61·50
0·9473	36·09	43	60·58
0·9456	37·00	44	59·54
0·9439	37·90	45	58·61
0·9421	38·82	46	57·64
0·9403	39·74	47	56·66
0·9385	40·66	48	55·68
0·9366	41·59	49	54·70
0·9348	42·53	50	53·72
0·9328	43·47	51	52·73
0·9308	44·41	52	51·74
0·9288	45·37	53	50·74
0·9267	46·33	54	49·74
0·9247	47·29	55	48·74
0·9226	48·26	56	47·73
0·9205	49·24	57	46·73
0·9183	50·21	58	45·72
0·9161	51·20	59	44·70
0·9139	52·20	60	43·68
0·9117	53·19	61	42·67
0·9095	54·20	62	41·65
0·9072	55·21	63	40·63
0·9049	56·23	64	39·60
0·9026	57·25	65	38·58
0·9002	58·29	66	37·54
0·8978	59·33	67	36·51
0·8954	60·38	68	35·47
0·8930	61·43	69	34·44
0·8905	62·50	70	33·39
0·8880	63·58	71	32·35
0·8855	64·64	72	31·30
0·8830	65·72	73	30·26
0·8804	66·82	74	29·20
0·8778	67·93	75	28·15
0·8752	69·04	76	27·09
0·8725	70·16	77	26·03
0·8698	71·30	78	24·96
0·8671	72·43	79	23·90
0·8644	73·59	80	22·83
0·8616	74·75	81	21·76
0·8588	75·91	82	20·68
0·8559	77·09	83	19·61
0·8530	78·29	84	18·52
0·8500	79·51	85	17·42
0·8470	80·72	86	16·32
0·8440	81·96	87	15·23
0·8409	83·22	88	14·12
0·8377	84·47	89	13·01
0·8344	85·74	90	11·88
0·8311	87·04	91	10·76
0·8277	88·37	92	9·62
0·8242	89·72	93	8·48
0·8206	91·08	94	7·32
0·8169	92·45	95	6·16
0·8130	93·89	96	4·97
0·8089	95·35	97	3·77
0·8046	96·83	98	2·54
0·8000	98·38	99	1·28
0·7951	100·00	100	0·00

(b) Solid residue.—This is determined by evaporating 100 c.c. of the liquor in a tared platinum dish, until constant weight is obtained.

(c) Ash.—The proportion of ash is found by the incineration of the solid residue. If the presence of poisonous metallic adulterants (such as copper or lead) is suspected, a further examination of the ash is necessary.

(d) Acids.—The acidity of distilled liquors is generally due to minute quantities of acetic acid, and can be estimated by means of 1⁄10th normal soda solution.

Any mineral acid (e.g., sulphuric acid) supposed to be present is to be sought for in the residue remaining, after the distillation process employed in the determination of alcohol.

The presence of fusel oil in liquors is sometimes quite readily detected, by first removing the ethylic alcohol by gentle evaporation, and then inspecting the odour and taste of the still warm residue. The suspected liquor may also be agitated with an equal volume of ether, water added, and the ethereal stratum removed by means of a pipette, and concentrated by evaporation; the residue is to be examined for amylic alcohol. When distilled with a mixture of sulphuric and acetic acids, amylic alcohol is converted into amylic acetate, which may be recognised by its characteristic pear-like odour; or, the amylic alcohol can be transformed into valerianic acid (which also possesses a distinctive odour) by oxidation with sulphuric acid and potassium dichromate. Another simple qualitative test for fusel oil consists in first decolorising a small quantity of the liquor under examination with animal charcoal, adding a few drops of hydrochloric acid, and then a little freshly distilled and colourless aniline oil, when, in presence of fusel oil, it will be observed that the aniline compound acquires a perceptible rose tint as it falls to the bottom of the liquid. The quantitative determination of fusel oil presents some difficulties. A very ingenious method has been suggested by Marquardt.[118] It consists essentially in first agitating the sample with chloroform, draining off the solution obtained, washing it by repeated shaking with water, and then treating it at 85° with a mixture of 5 parts potassium dichromate, 2 parts sulphuric acid, and 30 parts of water. The valerianic acid thus formed is now separated by distilling the mixture of water and chloroform. The distillate is digested with barium carbonate, next concentrated by evaporation, and then filtered, and divided into two equal portions. One portion is evaporated to dryness, the residue taken up with water containing a little nitric acid, and the amount of barium present determined by precipitation with sulphuric acid. In the other portion, the chlorine originating from a partial oxidation of the chloroform, is to be estimated. The amount of barium combined with the chlorine, is deducted from the total quantity obtained; the remainder represents the proportion in combination with the fatty acids formed by oxidation. Of these, valerianic acid largely predominates; and the amount of barium valerianate [Ba2 (C2H3O2)] found is calculated to its equivalent in amylic alcohol. Capsicum, creosote, etc., are isolated by treating the sample with ether or benzole, and testing the odour and taste of the evaporated solutions so prepared.