83 



ferring to filter paper. This method gave results which were in much closer agree- 

 ment, a- .-hown by the following results on the same sample: 



Per cent cat'fetannic acid 9.69 9.69 9.57 9.40 



Per cent lead 48.28 48.35 48.01 48.71 



Teefa made "ii a considerable quantity of the lead caffetannate washed in this 

 way .-howed it to be free from fat and nitrogen. 



It would seem as if the long pnx-ess of digestion with water and with alcohol pre- 

 scribed by Krug could be materially shortened. In much of our work extracts of the 

 (MII...- \>. . ; prepared by the use of a shaking machine, shaking the sample for an 

 hour with water and half an hour with alcohol. Results obtained in this way agree 

 very well with those obtained by the official method of digestion, although there is 

 e\ idem -c to -how that neither method extracts all of the caffetannic acid. 



Regarding the vexed question of the composition of caffetannic acid, we seem not 

 miieh nearer a -< -tt lenient . The views previously held, which seem to lead to the 

 formula for a di-glucosid, have been clearly set forth in Bulletin 105 by Mr. Howard. 

 Lack of time prevented any extended investigation of this problem, but an endeavor 

 was made to confirm the work of Cazeneuve and lladdon in regard to the di-glucosid 

 formula f.-r < arietannic arid. \\ e were unsuccessful, however, in preparing more 

 than traces of the osazone prepared by them, although carrying out the experiments 

 1 v in the manner prescribed. In this connection the paper recently published 

 by (i< t, in which the correctness of the Tazeneuve and Haddon 



formula i- que-t iu<-l < M>M. i -tales that he was unable to form more than a few small 

 cry-tal- ..f the o-a/.me, which he was unable to isolate and considered that it was 

 due t" -me impurity in the -aiTetannic acid. The caffetannic acid is considered 

 to be a mixture of chlorogenic and coffalic acids. Numerous derivatives 

 ami -all- of the-e arid- have been prepared and are described by the author to sup- 

 p..n hi- content 



Tin- methyl f..r carrying out the Krug test which we found to work most satisfac- 

 torily may be summed up as follows: 



me finely ground coffee (passing 0. 5 mm sieve), add 10 cc of water and shake 



i hur in a mechanical -halting device. Add 25 cc of 90 per cent alcohol and 



.-hake again f"r half an hour. Filter and wash with 90 per cent alcohol. Bring the 



united lili rat.- and about 50 cc, to boiling and add G cc of saturated lead 



- parate tin- precipitated lead caffetannate by means of a centri- 



intini: the -upernatant liquid through a tared filter. Repeat the centrifu- 



carineiit tui- with !M> per cent alcohol, decanting each time through the filter. 



the preen he filter and wash free from lead. Wash with ether, 



dry at iw j .and wciirh. The weight of precipitate multiplied by 0. 51597 gives the 



lit ..f cai'fetannic acid. 



CAFFEIN. 



In the work on caffein a comparison was made of three methods: The official 

 meth.nl (Bui. H>7, p. IMi; the titmtion of caffein with iodin, according to Gom- 

 in the tiltrate from tin- lead caffetannate; and the method proposed by Gorter 

 in tin- paper previously mentioned. 



Our attention ha.- been directed by Mr. C. D. Howard to a source of error in the 

 pp.vi-ional methyl, ari-ing from the fact that the extraction with dry chloroform 

 of the -aiid-ma-ne-ia mixture does not yield the whole of the caffein. Mr. Howard 

 says in his letter: 



My practice ha- been to add to the concentrated filtrate, contained in a tin-foil dish, 



about "10 Drains of sand and 1 gram of magnesium oxid, evaporate and dry in the water 

 The brittle ma-, easily stripped from the dish, I grind finely, 

 in a paper ext 



oven for a short time. l lie hrime mass, easny sinppeu uum tue ui<-n, &uim mmj, 

 place in a paper extraction cartridge, and extract for ten to twelve hours in the usual 



aAnnalen, 1908, 359: 217. 



