Oct. 24, 1884.] 



♦ KNOWLEDGE ♦ 



331 



V^ AN ILLAJf.T RATED '^^J^ 



MAGAZINE OF SCIENCE^ 

 PlmnlyWorded-ExactlyDescribed 



LONDON.- FRIDAY, OCT. 24, 1884. 



Contents op No. 156. 



PAGB 



The Chemistrv of Cookerv. XLV. i 



BvW.Mattieu Williams 331 I 



Notes on Coal. Bv K. A. Proctor.. 332 | 

 The Entomolopryof a Pond. (Ji/iMi.) 



Bv E. A. Butler 33-i 



Other Worlds than Ours 335 



Electroplatiug. By W. SlioRO 330 



Chats about Geometrical Measure- 

 ment. (Zi'a».) Bt B. a. Proctor 337 

 8eat and Footboard for Rowing- 

 boats. (///«».) 339 



How to Ride a Tricycle. By John 

 Browning 339 



PAGB 



Dickens's Story Left Half Told. 



By Thomas Foster 340 



Zodiacal Maps for the Month 342 



The Health Exhibition. XXI 343 



"Our Boys " in the Arena 3-14 



Editorial Gossip 315 



Reviews 346 



Face of the Skv. By F.B.A.3 346 



The Eclipse ot'the Moon 346 



Miscellanea 347 



Correspondence 34S 



The Inventor's Column 351 



Oor GhoBs Coltmm 352 



THE CHEMISTRY OF COOKERY. 



By W. Mattieu Williams. 



xlv.— cocoa and the cookery of wine. 



A COERESPONDENT writes to the Editor asking 

 t\. whether I cla«s cocoa amongst the stimulants. So 

 far as I am able to learn, it should not be so classed, but I 

 cannot speak absolutely. Mere chemistry supplies no 

 answer to this question. It is purely a physiological 

 subject, to be studied by observation of eflfects. Such 

 obsevations may be made by anybody whose system has 

 not become " tolerant " of the substance in question. My 

 own experience of cocoa in all its forms is that it is not 

 stimulating in any sensible degree. I have acquired no 

 habit of using it, and yet I can enjoy a rich cup or bowl 

 of cocoa or chocolate just before bed-time without losing 

 any sleep. When I am occasionally betrayed into taking 

 a late cup of coffee or tea, I repent it for some hours after 

 going to bed. My inquiries among other people, who are 

 not under the influence of that most powerful of all argu- 

 ments, the logic of inclination, have confirmed my own 

 experience. 



I should, however, add that some authorities have attri- 

 buted exhilirating properties to the theohromine or nitro- 

 genous alkaloid of cocoa. Its composition nearly re- 

 sembles that of theine, as the following (from Johnstone) 

 shows : — 



Theine. Theobromine. 



Caibon 4980 46-43 



Hydrogen 508 420 



Nitrogen 2883 3585 



Oxygen 16-29 1352 



100000 



100000 



It exists in the cocoa bean in about the same proportion 

 as the theine in tea, but in making a cup of cocoa we iise 

 a much greater weight of cocoa than of tea in a cup of 

 tea. If, therefore, the properties of theobromine were 

 similar to those of theine, we should feel the stimulating 

 effects much more decidedly. 



The alkaloid of tea and coffee in its pure state has been 

 administered to animals, and found to produce paralysis, 

 but I am not aware that theobromine has acted similarly. 



Another essential difference between cocoa and tea or 

 coffee is that cocoa is, strictly speaking, a food. We Ao 

 not merely make an infusion of the cacao bean, but eat it 

 bodily in the form of a soup. It is highly nutritious, one 

 of the most nutritious foods in common use. When 

 travelling on foot in mountainous and other regions, where- 

 there was a rifk of ^pending the night al fresco and 

 supperless, I have usually carried a cake of chocolate in my 

 knapsack, as the most portable and unchangeable form of 

 concentrated nutriment, and have found it most valuable. 

 On one occasion I went astray on the Kjolenfjeld, ha 

 Norway, and struggled for about 24 hours without food or 

 shelter. I had no chocolate then, and sorely repented my 

 improvidence. Many other pedestrians have tried chocolate- 

 in like manner, and all I know have commended its great 

 "staying" properties, simply regarded as food. I there- 

 fore conclude that Linnwus was not without strong justifi- 

 cation in giving it the name of theohroma (food for tlie- 

 gods), but to confirm this practically the pure nut, the 

 whole nut, and nothing but the nut (excepting the milk 

 and sugar added by the consumer) should be used. Some- 

 miserable counterfeits are offered — farinaceous paste, 

 flavoured with cocoa and sugar. The best sample I have- 

 been able to procure is the ship cocoa prepared for the. 

 Navy. This is nothing but the whole nut unsweetened^ 

 ground, and crushed to an impalpable paste. It requires 

 a little boiling, and when milk alone is used, with due 

 propoi'tioa of sugar, it is a theohroma. Condensed milk 

 diluted and without farther sweetening may be used. 



In my last I promised the results of my investigations- 

 concerning the source of the sulphate of potash that I 

 found replacing the natural tartrate in so many samples of 

 sherry. 



At first I hunted up all the information I could obtain 

 from books concerning the manufiicture of sherry, learned 

 that the grapes are usually sprinkled with a little powdered' 

 sulphur as they are placed in the vats prior to stamping. 

 The quantity thus added, however, is quite insufficient to- 

 account for the sulphur compounds in the .■samples of wine 

 I examined. Another source is described in the books 

 — that from the sulphuring the casks. This process con- 

 sists simply of burning sulphur inside a partially-filled or 

 empty cask, until the exhaustion of free oxygen and iis 

 replacement by sulphurous acid renders fut'ier combnstioii 

 impossible. 'J'he cask is then filled with the wine. This- 

 would add a little of sulphurous acid, but still not sufficient. 

 Then comes the " plastering," or intentional addition of 

 gypsum (plaster of Paris). This, if largely carried out, is ■ 

 sufficient to explain the complete conversion of the naturaif 

 tartrates into sulphates of potash, but such plastering is 

 admitted to be an adulteration or sophistication, and the- 

 best makers deny their use of it. I obtained samples of 

 sherry from a reliable source, which I have no doubt the- 

 shipper honestly believed to have been subjected to no suchi' 

 deliberate plastering ; still, from these came down an ex- 

 travagantly excessive precipitate on the addition of chloride 

 of barium solution. 



At last I learned that " Spanish earth " was used in the- 

 fining. Why Spanish earth in preference to isinglass or- 

 white of egg, which are quite unobjectionable and very- 

 efficient 1 To this question I could get no satisfactory: 

 ans-wer directly, but learned vaguely that the fining pro^ 

 duced by the white of egg, though complete at the time^ 

 was not permanent, while that effected Vjy Spanish earth,, 

 containing much sulphate of lime, is permanent. The 

 brilliancy thus obtained is not lost by a.%e or variations of 

 temperature, and the dry shen-ies thus cooked are preferreti. 

 by English wine-drinker.*. 



Here, then, is a solution of the my.'-tery. The su?pilat»' 



