304 PRACTICAL PHYSIOLOGY 



gives amount of free fatty acids present. Calculate the oleic acid by 



N 

 multiplying number of c.c. ^ NaOH required by 0-0282. 



(3) Brush off the residue in the mortar and on the filter paper into a 

 beaker. In order to get every trace of material from the filter paper 

 to the beaker pierce the bottom of the filter, wash once with boiling 

 water, then moisten it with a few drops of concentrated HC1. Wash 

 repeatedly with boiling water until every trace is in beaker. Add HC1 

 up to 10 per cent. Place beaker on a boiling water bath for two hours. 

 Cool. Pour into a separating funnel and extract three times with ether. 

 Wash the ethereal extract three times with small amounts of water. 

 Place ethereal extract in a weighed flask, distil off the ether, dry and 

 weigh. Result = combined fatty acids. 



Estimation of Carbohydrate. Take 20 gms. of dried faeces and 

 place it in an Erlenmeyer flask (300 c.c. capacity) with 100 c.c. 2 per 

 cent. HC1, connect with a reflux condenser and boil for one and a half 

 to two hours. Almost neutralise and then filter into a litre flask, 

 washing the residue on the filter paper thoroughly, and make up to 

 1 litre. The sugar present may either be estimated by a titration 

 method or preferably by a gravimetric method. Place 60 c.c. of freshly 

 mixed Fehliiig solution in a small Erlenmeyer flask arid immerse the 

 flask in a boiling waterbath. When the Fehling solution has attained 

 the temperature of the boiling water add 20 c.c. (which should not 

 contain more than 0-25 gm. reducing sugar, check by a rough analysis 

 beforehand) of the solution to be tested, previously warmed, and make 

 contents of flask up to 100 c.c. by the addition of boiling distilled water. 

 The mouth of the flask is lightly plugged with cotton wool and the 

 heating continued for exactly twelve minutes. At the end of the period 

 the flask is removed from the bath and the contents filtered through 

 asbestos 1 in a Gooch crucible. Wash well with hot water, taking care 

 that all traces of cuprous oxide are transferred from the flask to the 

 crucible, then with alcohol and ether. Dry quickly in a hot-air oven, 

 cool and weigh as cuprous oxide. If the Gooch crucible containing the 

 cuprous oxide be placed in a protecting nickel crucible and heated by 

 means of a powerful burner for thirty minutes the cuprous oxide is 

 oxidised to cupric oxide. Continue heating until weight is constant. 

 Cool and weigh. The cuprous oxide can also be, if preferred, reduced to 

 metallic copper by gentle heating in a stream of hydrogen. Cool and 

 weigh. 



Calculation of results Weight of pi'ec'pitate as 



Copper X -5638 \ 

 Cuprous oxids X -5042 - amount of sugar (as dextrose) present. 



Cupric oxide x -4535 J 



Estimation of Calcium. Take 5 gms. of the fseces and ash it in a 

 small silica crucible (if platinum is not available). Transfer the ash to a 

 500 c.c. measuring flask, washing in the last traces with dilute HC1. 

 When the ash in the flask has all dissolved in the HC1 make up with 

 distilled water to the 500 c.c. mark. Draw off 200 c.c. into a 600 c.c. 

 beaker and add a slight excess of ammonia until a precipitate of calcium 

 phosphate appears, then add acetic acid until the solution is faintly acid 



1 The asbestos used in preparing the mat in the Gooch crucible should 

 be specially purified by treatment with hydrochloric acid. All hard lumps 

 should be removed. The same crucible can be used for many analyses. The 

 mat should be about 2 mm. thick. 



