140 REPORTS ON INVESTIGATIONS AND PROJECTS. 



CHEMISTRY. 



Acree, Solomon F., Johns Hopkins University, Baltimore, Maryland. Grants 

 Nos. 204 and 372. Study of pinacoyie-pinacolin r-earrangement and of 

 urazoles. (For previous report see Year Book No. 4, pp. 134-135.) 



$1,300. 



Report. — Dr. Acree has continued the investigations on the pinacone 

 rearrangement and the urazoles. The work on the urazoles will be reported 

 on later. In the study of the pinacone rearrangement, a phase of this sub- 

 ject, of biological importance, was taken up in conjunction with Dr. J. E. 

 Hinkins in the investigation of some cases of abnormally acid saliva. It 

 was thought possible that carbohydrates in the saliva undergo a rearrange- 

 ment into the acids found to be present. 



A number of individuals suffering from erosion of the teeth, attended with 

 abnormally acid saliva, presented themselves to aid in the work. The saliva 

 was titrated with N/ 10 potassium hydroxide solution and phenol phthalein 

 and found to vary with the different individuals from N / 300 to N / 50. An 

 increase in the acidity of the saliva was attended by an increase in the 

 severity of the erosion of the teeth. Investigations were made to throw 

 light upon the following questions: (i) Is the acid generated wholly or 

 partially in the saliva by aerobic or anaerobic bacteria present in the mouth ? 

 (2) Is the acid generated appreciably by enzymes present in the saliva ? (3) 

 Is the acid generated entirely or in part in the mouth or does the saliva issue 

 acid from the ducts ? 



(i) A study of the rate of formation of acids by various mouth-bacteria, 

 such as B. coli communis, Staphylococcus pyogenes aicreus, etc., in different 

 culture media led to the conclusion that bacteria are hardly at all concerned 

 in the formation of the acid in the saliva. 



(2) Similarly, a study of the rate of hydrolysis of triacetylglucose by 

 various enzymes led to the belief that enzymes play only a very small role in 

 the generation of acid in the saliva after it enters the mouth. 



(3) A study of samples of saliva obtained from different individuals by 

 catheterizing the left Steno's duct showed this saliva to be as acid as the 

 total saliva obtained from the mouth. A bacteriological examination of the 

 saliva issuing from the ducts of the different individuals showed these salivas 

 to be free from bacteria. The conclusion, then, is that the saliva is secreted 

 acid in the glands. 



In the further study of erosion of tooth structure some new analyses of 

 teeth were made, and a new color test for proteids was investigated. The 

 results of these researches are embodied in three articles, now ready for pub- 

 lication, which will appear with the titles "On Abnormally Acid Saliva," 

 "On the Composition of the Dentine and Enamel of Human Teeth," and 

 "A Formaldehyde Color Test for Proteids (I)." The investigations will 

 be continued. 



