R E C E N T P R O G R E S S IN T H E ANALYSIS OF C A T T L E FOODS.' I % \ 1;
0
\v
\V are ignited i i i a muffle oven a t as low teiiiperature as possihle, and the crude ash weighed, carbon dioxide and char are then deterniiiicd in a portion of the crude ash, and corrections niade accoi-tlingl)-. 3 . Protein .--Deteriiiiiiatioii of iiitrogeri and using the factor 0.2j.
4. Crudt Fiber.-&\ quaiitit!. corresponding to three grains water-free substance is takeii, and heated for oiie-half hour in a flat porcelaiii tlish with -700cc. of a I: per cent. sulphuric acid solution, adding water as it boils away : t h e solution is then left to settle and the clear liquid pipetted off into a beaker; the saiiiple is again ljoiletf for one-half hour with water, the clear liquid pipetted off into the same beaker as before, and the operations of hoiling with :'uo cc. of n-ater aiitl pipettirig off repeated a secoiicl time. 2 0 0 cc. of a I i. per ceiit. potassiuin hydroxide solution are then added and boiled for linlf a n hour, tlie clear liquid pipetted off into a second beaker, tlie residue boiled twice with ZOO cc. of water, each time uniting the liquid with that already i n the second beaker. T h e residue is then brought on a filter arid also that which has settled in the beaker containing t h e alkaline fluid; the filter is washed until neutral reaction, when the residue in the other beaker is added and the washing repeated and finished by 1
Kead bcfot-e the World's Collyress of C h e r o i a t s , h u g u i t 24. IYyj.
PROGRESS IS A S A L Y S I S OF C.1TTLZ FOODS.
'75
successive washings with alcohol aiid ether, drying, weighing. and incineration, which gives the crude fiber by difference. j . Ether Exti-nrt (fat). -Complete extraction with boiling anhydrous ether, distillation of the united filtered distillates, and drying the residue at 100-1IO' C . Since these methods were first published, our knowledge of the composition of plants and feeding stuffs has been greatly widened ; we understand far better than did the writers thirty years ago, what, the various groups separated out by the Weende experimenters include, aiid the conditions which inust be observed in each case in order to obtain correct results. But on the purely analytical side we have made but very little progress ; the probleiiis have grown more complex every year, and the difficulties of the problems have increased niucli faster than has our ability to meet them. I n giving a short account of the progress made during recent years in the aiialysis of cattle foods, I shall take up the various components iii tlie order adopted by Henneberg and still followed by agricultural chemists i n general, and shall show the changes which the methods have undergone and suggest the reasoii for these changes. As sho\\n by \YiIiii, Baliriiig, Raessler, and others, nzoistwc caiiiiot be cleteriiiiiieti i i i iiiaiiy of our food stuffs by a siniple drying iii the air, as the fat coiitaiiied iii them will oxidize and the saiiiple thus iiicrease i i i weiglit, which iiiearis a too low percentage of moisture. Desicc:ition must, therefore, be conducted in tlie iiiediuiii of an iiidifferent g a s ; the gas now generally adopted for dryiiig is 1i)drogeii or carbon dioxide, preferably the former. lfarcker has further slion-11 that drying above 100' C. may cause fornintioii of resiiious substances, aiid Jenkins found that a volatile oil). matter passed off when fodders were heated at I 10' i i i the air or i n other g-nses : tlie saiiie was obsen-ed by Baessler, IViley, and Cutter. The teiiiperature ought, therefore, never to exceed 100' C . T h e tiiiie necessary for drying will depeiitl 011 tlie kind of apparatus iised arid will vary from four to teii hours; iii case of a dry current of hydrogen being passed through the saiiiples, four to six hours will as a rule be found necessary, the velocity of tlie current being the deciding factor
as to tlie time required; go to IOO bubbles of hydrogen per iiiiiiute is a iiiaxiiiiuiii velocity (Xiidersoii). T h e loss of volatile substances will be increased wheii a very rapid current is passed through the saiiiple. II'lierc. the fodders are heated on or i i i opeii disks i i i aii atmosphere of hydrogen, longer time u.il1 be iiecessar!. thaii otlierwise, sometiiiies as much R S ten hours, tlie temperature of tlr!.iiix being all the time tliat of boiling water. Gfhrr /
