84 CHEMICAL PHYSIOLOGY. 



2. Chlorides are chiefly those of sodium with a little potassium 

 and ammonium, derived chiefly from the food, and amount to 

 10 to 15 grammes (150 to 230 grs.) 



(a.) Test with a few drops of AgNO 3 (1 pt. to 8 distilled 

 water) = white, cheesy, or curdy precipitate in lumps in- 

 soluble in HNO 3 . The phosphate of silver is also thrown 

 down, but it is soluble in HNO 3 . 



Variations, increased in amount when the urine is secreted in 

 excess, although the NaCl usually remains very constant (| per 

 cent.); lessened in febrile affections, and where a large amount of 

 exudation has taken place, as in acute pneumonia, when chlorides 

 may be absent from the urine. The reappearance of chlorides in 

 the urine is a good symptom, and indicates an improvement in 

 the condition of the lung. N.B. The urine ought to be tested 

 daily for chlorides in cases of pneumonia. 



(6.) Test urine from a case of pneumonia, and compare 

 the amount of the precipitate with that of a normal urine. 



Estimation. A rough estimate may be formed of the amount 

 by allowing the precipitate to subside, and comparing its bulk 

 from day to day. 



3. Sulphates are those of soda and potash. Quantity 3 to 4 

 grammes (46 to 61 grs.) They have no clinical significance. 



(a.) Test with a soluble salt of barium (the nitrate or 

 chloride) = white heavy precipitate of barium sulphate,, 

 insoluble in HNO :J . 



4. The Phosphates consist partly of alkaline and partly of 

 earthy salts in the proportion of 2 to 1. The latter are insoluble 

 in an alkaline medium, and are precipitated when the urine 

 becomes alkaline. They are insoluble in water, but soluble in 

 acids ; in urine they are held in solution by free CO 2 . The 

 alkaline phosphates are very soluble in water, and they never 

 form urinary deposits. 



5. The Earthy Phosphates are phosphates of lime and mag- 

 nesia. Quantity 1 to 1-5 grammes (15 to 23 grs.) They are precipi- 

 tated when the urine is alkaline, although not in the form in 

 which they occur in the urine (Lesson XIII., 10). They are 



