METHODS OF ANALYSIS. 33 



fed organic phosphorus. This was made into a thick paste and placed 

 on a Miiall tray in one corner of the cage. The same procedure \vas 

 followed in the case of the rabbits fed inorganic phosphorus, except 

 that instead of phytin the salt solution containing the inorganic 

 phosphorus was mixed with the food. Thus the rabbits wen 4 com- 

 pelled to eat the food containing the phosphorus before the remain- 

 der of the food was given to them. The rest of the carrots, sugar 

 and >tarch mixture, and 2 < of olive oil were made into a thick 

 paMe and given to the rabbits during the afternoon. 



METHODS OF ANALYSIS. 



Fach rabbit was confined in a suitable wire cage, which allowed 

 the feces and urine to be easily separated. 



After establishing a nitrogen equilibrium, the experiments with 

 the rabbits were commenced. The focefl \\ere collected at fre(iueilt 

 interval- during the day. OWmg to the fact that the rabbits persist- 

 ently ate them. The urine and the food reMduo were collected 

 daily. All of the-e >ample- ueie composited and analy/ed; the 

 nitrogen in the food. fece-. and urine being determined according to 

 the (limning ' method a;nl the phosphoric acid in the food, feces, 

 and urine by Neumann'- '' method. The phosphoric acid in the 

 urine ua- determined aUo by the uranium acetate volumetric 

 method. In this \\-.i\- a check on the amount of phosphoric acid in 

 the urine was obtained, and further, this double determination 

 Sen <'d a- an indication of the presence of organic pho^phoru-. 



The methods employed for \\ater and a-h. ami for calcium and 

 magnesium' were tho-e of the Aociation of Ollicial Agricultural 

 Uicmi-K. From ~2 to :i gram- of the food- or fecefl wm a-hed; and 

 in the ca>e of the urine. 'Jnn <-. \\ere e\ aporatecl to dryne-> iii a plati- 

 num di>h and allied. The ether-alcohol soluble phosphorus (lecithin) 

 determined in the following manner: 



'I'r.in-i'.T MI,,- ,, r m ..f ih.- tiin-ly -^n.uinl .-nl.-lanc- \n u :!(-<< 



lla.-k: a-1'1 :'.' OC "I al>-..lut.- .-ili.-r ami -xira-i iht- wh..|,- <,\.-r niu'hi. l-'iltrr 



i thmuu'h a hanlfiit-d tiltrr pajn-r int<> an ordinary .Jnui flat-bottomed flask of 

 503-cc capacity ami ivttirn any |>articli- of ih,- r->iilu- fotind on the fill* r paper to the 

 Hrlenmeyer Jla.-k. Then a<ll to th- nh-T extract residue 60 cc of ab.sulute alcohol 

 .uul boil the solution for three hours, u.-in-j a reflux condenser. Filter this alcohol 

 extract while hot into the . I. -na tla-k containing the ether extract and wa.-h tin- re-idue 

 t\vic with two separate port io;. f liot alcohol, adding the wa.-h in-^ to the 



extract. In the combined fth-r-ali-ohol filtrate determine the phosphoric acid by the 

 Neumann f > method. 



o U. S. I)eju. A-r.. P.un-au of < 'h.-miMry, Hul. 107, Rev., p. 7. 



ft Zts. pliv.Mol. Ch.-in.. 1 '.MIL'. 57 : 11"). 



c\ \-r.. Bureau. .f Chemistry, Hul. 107. R.-v., p. i:,. Hi. 



77400 Hull. 123-09 3 



