PIPE COVERING AND CEMENT. 61 



6. Other Tests. 



Ash a 10 grain portion of the disinfectant and determine the alkalinity of 

 the ash, and whether the alkali is soda or potash. 



In determining the relative values of disinfectants of this class, the sample 

 should be submitted to a bacteriological test. In the absense of such a test 

 the substance may be graded by the sum of the percentage of phenols and 

 pyridiu. This is, of course, only a general approximation, as the hydrocarbons 

 and soaps doubtless have some germicidal action. 



PIPE COVERING AND CEMENT. 

 1. Sampling. 



The insulating covering for steam pipes is generally made of a hydrated basic 

 carbonate of magnesium and serpentine asbestos. Such material is difficult to 

 sample, but by cutting out pieces of about 1 gram weight from 12 or more 

 different places on the section of pipe covering, grinding in a mortar and thor- 

 oughly mixing, a satisfactory sample can generally be obtained. Preserve this 

 sample in a tightly stoppered bottle. 



The cement for pipe covering is of the same composition as the cover itself 

 and is examined in the same way, but it is much easier to sample. 



2. Moisture (Loss at 105 C.). 



Dry 1 gram of the prepared sample for two hours at 105 C., weigh, and 

 calculate loss in weight as moisture. 



3. Loss on Ignition. 



Ignite sample used for the moisture determination to constant weight. It is 

 necessary to stir the material several times to insure heating all parts of the 

 sample. 



4. Asbestos. 



Treat 5 grams with 100 cc of 6 per cent acetic acid, heating on the steam 

 bath to hasten solution. Filter on a Gooch crucible, wash, dry at 120 to 

 130 C., and weigh. This result is considered to represent asbestos. Then 

 ignite to determine the water in the asbestos (about 14 per cent generally), 

 which is deducted from the total, as it has already been included in the " Loss 

 on Ignition." By this method all matter insoluble in acetic acid is assumed to 

 be asbestos. If the presence of other insoluble material is suspected, filter on 

 paper and examine the residue with the microscope or make an analysis of it. 

 This, however, is seldom necessary. Serpentine asbestos is slightly soluble in 

 acetic acid, but this error may be neglected. 



5. Alumina and Iron Oxid. 



Add ammonium chlorid and ammonium hydroxid to the filtrate from the 

 asbestos, filter, dissolve precipitate in hydrochloric acid, reprecipitate with am- 

 monium hydroxid, filter, wash, ignite, and weigh as alumina and iron oxid. 



6. Magnesia. 



Unite the filtrates from the alumina and iron oxid and make up to 500 cc. 

 On 25 cc of this solution determine magnesia in the ordinary manner. If 



