[Read at the meeting in May, 18-7.]

Hitherto the detection of hop substitutes in beer has had for English analysts little more than an academic interest. There has been no definition of beer, nor standard of strength or quality, and hence the brewer has been free to employ any hop substitute that could fairly be regarded as non-injurious. Now, however, that there are two bills before Parliament, both of which aim at rendering the employment of hop substitutes illegal, unless duly acknowledged, the question has acquired considerable practical importance. If the bills in question ever become law, it will devolve on the public analyst to certify to the presence or absence of hop substitutes, but, as was recently pointed out by the chancellor of the exchequer to a deputation which waited on him, it would be of no use to pass an act forbidding the unacknowledged use of hop substitutes unless it was possible to detect infringement of the law. Hence it has become important for public analysts to see how far the more important hop substitutes can be definitely detected in beer, or at any rate distinguished from hops.

The problem in question is by no means a simple one. Beer itself is a highly complex and variable product, and some of the normal constituents add to the difficulty of detecting hop substitutes. The problem is further complicated by the possible presence of several substitutes simultaneously, together with actual hops. Then the bitter principles to which the hop substitutes owe their employment have in some cases been very imperfectly studied, and belong to a class of bodies by no means distinguished for strong chemical affinities or for characteristic reactions. In fact,the most gennral and striking property of the majority of hop substitutes is the intensity of their bitter taste, a character which materially increases the difficulty of detecting them, owing to the very moderate amount employed to give the beer the desired flavor. There is one other complication of practical importance, and that is the very considerable quantity of beer usually recommended to be used for the analysis. Thus, if two liters be used for the main examination, as is recommended by Dragendorff, at least twice that quantity should be submitted to the analyst, and hence twelve liters would have to be purchased. The necessity of purchasing so large a quantity as two and a half gallons of each beer would almost certainly render the act abortive.

1 Analyst 1887, p, 79.

2 Ibid., p;07

In looking into the question, therefore, I have aimed at reducing the amount of beer employed as low as possible.

In the last number of the Analyst I gave a list of references to articles in English periodicals, etc, connected with detection of hop substitutes in beer. These I have carefully studied, and they have formed the foundation of the following statements and proposals:

Dragendorff, who has published a very elaborate method for the recognition of a large number of possible hop substitutes (Jour. Chem. Soc., XXVII, 818; XLII, 103), operates on two liters of beer, precipitates the concentrated liquid with basic acetate of lead, further concentrates the filtrate and adds a large volume (1,000 to l,200cc.)of absolute alcohol. The spirit is subsequently driven off, and the various principles extracted by a systematic employment of immiscible solvents.

Wittstein (Jour. Chem. Soc, XXIX, 767) operates in a similar manner, but works on one liter, and omits the treatment with acetate of lead, as indeed did Dragendorff in his older method. In the method described by me in my Commercial Organic Analysis (Vol. I, page 97), based on a process of Ender's, one liter of beer is employed, the concentrated liquid is treated with alcohol, the filtrate precipitated with ether, and the filtered liquid evaporated, the residue redissolved in alcohol, treated with water, and the solution precipitated with acetate of lead.

Several of the writers on the subject state that on precipitating a beer with basic acetate of lead the hop-bitter is wholly precipitated, and hence, if the concentrated filtrate still have a bitter taste, the presence of some hop substitute is certain.1

This difference seemed to me so important that I have very carefully investigated it, and find it perfectly in accordance with the fact. I prefer, however, to employ neutral acetate of lead instead of the basic or ammoniacal acetate, as the latter reagents are liable to precipitate certain bitter principles not removed by the first. On the other hand, the hop-bitter is very perfectly precipitated by neutral lead acetate, and this statement is equally true of an infusion of hops purposely prepared and of a beer in which hops is the sole bitter used; but I have some reason to think that basic acetate of lead is liable to effect a less perfect separation of the hop-bitter.

In attempting to improve these processes I have endeavored to dispense with the use of alcohol, and yet separate the bitter principles from the sugar and other bodies which disguise the bitter taste and interfere with application of chemical tests, and find that a very satisfactory product for further treatment can be obtained by the following simple method:

One liter of the beer is evaporated to about 300cc. and is then precipitated, while hot, with a solution of neutral acetate of lead. The precipitate is filtered off, the filtrate allowed to become cool, and any further precipitate is also removed. The excess of lead is then removed from the filtrate by sulphuretted hydrogen, and the liquid filtered and further concentrated to about 150cc. I prefer sulphuretted hydrogen to sulphuric acid or a sulphate, as the lead sulphide seems to carry down a notable quantity of coloring matter.

1This distinction between the bitter principles of hops and hop substitutes is referred to in the work entitled Chemistry Applied to the Arts and Manufactures, edited by Chas. Vincent, and often described as the New Edition of Muspratt's Chemistry. The process is also described in Wynter Blyth's work on the Analysis of Food, and forms an essential part of Ender's method of detecting bitter substances, so that there is a very general consensus of opinion as to the value of the test.