LITERATURE

ASCHER OPLER, The D o w Chemical Co., Pittsburg, California

Dow Refines Structural Searching Along with a couple years testing experience have come changes and additions to Dow's search program

S O M E four and one half years ago, T. R. Norton and I began developing a system for searching coded chemical compounds for desired structural fea­tures. We have already told the story of t h e successive stages and develop­ment of the systeui up to mid-1955 (C&EN, J u n e ' 4 , 1956, page 2812) . We have also distributed quite a few copies of a manual for coding and a manual for programming.

What I propose to do here is describe the many interesting developments that have taken place in the last two years and mention some new approaches to machine searching that we have ex­plored and that we feel are significant.

First, a few words about the com­puter we have selected. Our experience has shown that cost per search de­creases rapidly with increasing size of the computer. Our whole develop­

ment has been toward larger and faster machines. Today, we are basing our search work entirely on the IBM 704, a digital computer. This does not ex­clude the use of other high speed ma­chines, nor does it exclude the possi­bility of using intermediate size ma­chines such as the IBM 650 and the Datatron. However, the logical abili­ties and the input-output system of the 704 St it well to this problem.

THE COMPUTER. The IBM 704 operates in the binary num­ber system. It carries out logical operations at speeds of roughly two and one half million simple operations per minute. In addition, six or more magnetic tape units can

serve as input to and output from the machine. Since the tape units "read and write" at extremely high speeds, the computer is not slowed down by its input and output— often the case with smaller machines

9 2 C & E N A U G . 19. 1957

The Computer Program

O n e reel of magnetic tape will hold the contents of 40,000 to 50,000 fully punched, 80-column punched cards. If the cards are not fully punched, the tape will hold proportionately more. One reel of this tape , therefore, can contain the serial number , empirical formula, and complete structural code lor S0,000 to 100,000 typical organic-compounds.

Thus , structural information for one million compounds can be stored in a single file drawer of conventional letter size. Information properly stored is permanent. It may be transcribed quickly to a new tape ; the machine requires roughly four minutes to dupli­cate and completely check a tape con­taining 100,000 chemical structures.

Star t ing about a year ago, we began to wri te a general searching program. This has been tested and is now opera­tive. (Most of the machine work was done at IBM's New York Data Proc­essing Center.)

T h e program consists of some 2000 computer instructions, contained in a deck of approximately 100 binary-punched cards, each containing up to 22 instructions.

Before starting on the 704 work, we converted all the chemical structure codes that we already had on punched cards to magnetic tape. We learned a lo t from this conversion. By actual count, t h e tape contained the struc­tures of 10,585 chemical c o m p o u n d s -less than one eighth of one tape reel.

I n transcription from cards to tape, we m a d e a number of worthwhile for­mat changes. All blank spaces have been eliminated, structures whose com­plexity required several punched cards have been condensed, and finally, the structure codes have been "blocked" into aggregates of approximately 120 compounds. The advantage of block­ing will appear later.

The Multiplexing Principle

Before going into the computer op­eration any further, I would like to digress and discuss what we term multiplexing. This name is borrowed from the communications field where it refers to transmission of a number of different messages simultaneously over a single circuit. These messages are chopped into small segments which are sent alternately and then resynthe-sized at the other end. In applying this principle to searching, we conduct a number of simultaneous searches on

704 SEARCH REQUEST FORM

> • £ *T i?<

L. U^C-gV-t>--VwZ^flh/u^.

°»^ V-

xi , 7 ._

L^iwl^gf i^ -^

i i y . o i l i o 4 . o i t3»,£>i i , * o »

A chemist's search requirements end on • this form—a re­

quest} for ̂ search.,0 It - Z. takes only VV few. > minutes to fill out *

o

x z.

o

\ 3

/ | o | i () t J 1 O

/H i U

i

o

J

f T H 1 id

STATISTICS d

the coded structures by actually alter­nating the different searches, and, at the conclusion, separating the results for each search.

T h e advantage of multiplexed searches may not be obvious a t once. Since there is no statistical sampling involved, w e must compare every coded structure with every set of search requirements. If there are n structures and m searches to be performed, a total of nm comparisons must always be made.

T h e classical approach has been to take each search and then to compare each of the n structures with it. An alternate if impractical approach would be to take each structure and see if it satisfies any of the rn search requirements. T h e multiplexed ap­proach consists of taking the m searches, p at a time, and comparing them with t h e n structures, q at a time.

T h e advantage to be gained by this ostensibly clumsy handling of struc­tures and search requirements lies en­tirely in practical questions involving computer operation. The slowest op­eration in searching is the input step, and any gain in over-all speed will almost certainly b e by reducing input time.

In general, the size of p and q will be determined by the speed and ca­

paci ty of the computing machine and the relative input speeds . For our particular structures a n d a standard IBM 704, we have selected p to be 5 and q to b e approximately 120. It is for this reason that the structures on t ape have been blocked into groups of 120.

This , then, is the rhy thm of search:

• One block of 120 words is read from tape to computer .

• Search No. 1 is swi tched on by the machine and conducted for these 120 structures.

• Any successful results are written on tape in a special block labelled with the identity of Search N o . 1.

• Additional searches up to five are automatically switched in successively.

• At the conclusion of the last search, a block of 120 new structures is read from the input tape.

• The above steps are now repeated until the end of the input tape is reached.

Request Cards

T h e p search requirements are fed to the computer in the form of "request cards," one of which is prepared for each search. In 72 columns, the card contains all the information needed to

A U G . 19, 1 9 5 7 C & E N 9 3

• >%V^*4 W However, the number of hydrogens i.s never a criterion.

When the compound under examina­tion has met the empirical formula re­quirements, the computer examines its component groups. T h e original re­quest may specify up to four of the 330 groups used in the Dow code and may call for a minimum of up to nine of each group. For example, a specific search may call for two benzene rings, one ether group, two nitro groups and five monochloro groups. The com­pound will be rejected if any criterion is not met. In posing the search ques­tions, it is desirable, but not obligatory, to ask for the least common group or element first, so that rejection may occur as early in the process as possible.

The search beg in s with three items at hand—deck of computer instructions, search request cards (one for each search), and magnetic tape of structures

specify requirements for a single search. Thus , analysis of the search requirement leads to filling out the re­quest sheet f o r subsequent key punch­ing and loa<l; % into the computer. Translating t l i e chemists' requirements into one of tkiese forms is easy to learn and requires less than five minutes to do.

W h e n the search begins, we have - three items t o be loaded in or near t h e computer. These are t h e program deck (instructions for carrying out a structural search) y five (or less) search request cards, and a reel of magnetic tape containing the structures to be searched.

W e have r u n a large number of mul­tiplexed searches in checking out the searching program, in studying how the program performs, and in running actual searcties. The average time re­quired for search of 10,585 compounds with five-fold multiplexing is about six minutes—one minute and 12 seconds to search over ten thousand compounds exhaustively .

In its present form, the program per­mits four Jifferent types of output for search results:

• Direct punching of cards with serial number .

• Writing of magnetic tape which is later used t o produce punched c a r d s -called peripheral output.

• Printing of the identifying serial numbers peripherally.

• Printing the chemical names found by each seaxch o n a separate list.

Search Criteria

In addition to the input , output and multiplexing portions, there are four major parts of the program—the criteria to be met. In our setup these are:

• Empirical formula. • Component groups. • Direct connections between groups. • Indirect and positional attachment.

We fit t he empirical formula criterion this way. In our program, we can specify the number of carbon atoms and three elements from the group N, O, P, S, F , CI, Br, and I. In the former case, a limit of 99 atoms may be speci­fied and, in the latter case, nine. By means of a suitable punch, the number given may be the minimum or the exact number to be present in the compound.

Group Size

Again, 1 must digress to describe our approach to a perplexing problem. What is the optimum size of chemical groups to be used in searching? We have long debated whether we should code and search by very small groups —or even single atoms—or by very large general groups. Since coding by either of these two extremes has led to dis­satisfaction in the past, we selected chemical groups of intermediate size. Thus, we rejected the idea of coding the benzene ring as six C1 groups and we also rejected the idea of having benzoic acid as a group.

Many requests are received in gen­eral terms. For example, the chemist desires a list of al l dialkylamino-phenols. Since the term "alkyl" in­cludes a number of o u r groups, it ap­pears that we could handle the problem only by running repeated searches. Since we have thirty groups which are classed as alkyls, and the term dialkyl

9 4 C & E M A U G . I9,v 19 57

is not res t r ic ted to symmet r i ca l dialkyl , w e w o u l d n e e d 870 searches to collect an exhaus t i ve list.

T o get a r o u n d this , we h a v e intro­d u c e d t h e c o n c e p t of a "c lass" as a col lect ion of r e l a t ed g roups . T h u s the class "alky!" consists of methyl , e thyl , p ropy l , e tc . , a n d the class " a m i n e " con­sists of p r i m a r y , s econdary , ter t iary , a n d q u a t e r n a r y amines .

T h e c o m p u t e r p r o g r a m recognizes w h e n a r e q u e s t e d " g r o u p " is not a g r o u p h u t is ac tua l ly a class. W h e n this recogni t ion is m a d e , the c o m p u t e r logic is c h a n g e d so that it examines e a c h g r o u p b e l o n g i n g to that class and rejects t h e c o m p o u n d only if none ot t h e s e g roups is found . in the c o m p o u n d u n d e r examina t ion? G r o u p s ' ' and

• classes may h e freely in termixed and , * in all p r o b l e m s involving connec t ions a n d posi t ions , the m e m b e r of a class is t r e a t e d exact ly as if it w e r e a speci­fied g r o u p . T h u s , in search ing for c l ia lkylaminophenols , methyl and octyl g r o u p s will b o t h be selected as alkyls a n d , in t h e s u b s e q u e n t examinat ion to d e t e r m i n e if they a r e a t t a ched to the a m i n o g r o u p , will b e t rea ted as equ iva ­lent alkyl g r o u p s .

Direct Connection

T h e th i rd cr i ter ion is direct connec ­tion b e t w e e n t w o g r o u p s . Any t w o of the four g r o u p s u sed in t h e previous por t ion of the p r o g r a m may b e selected as a pai r . T h e p r o g r a m will ins t ruct the c o m p u t e r to d e t e r m i n e w h e t h e r or not these g r o u p s are direct ly connec ted toge the r . Mu l t i p l e connec t ions are often specif ied in t h e search, so we often g e t t w o s t ruc tures wi th t he re­q u e s t e d d i rec t connect ion bu t with o the r differences. For example , these two s t r uc tu r e s :

(1

CI

CI CI

I> •/

both con ta in two direct connec t ions b e t w e e n b e n z e n e a n d a ch lor ine , but the c o m p u t e r can h e p r o g r a m m e d to reject o n e a n d accep t the o ther .

In g e n e r a l , we a re in te res ted in s t ruc tu re s t h a t con ta in a m i n i m u m n u m b e r of a cer ta in type connect ion , but often w o wish to specify an exact n u m b e r ol c o n n e c t i o n s . T h e c o m p u t e r p r o g r a m can h a n d l e this, too. Direct connec t ions c a n be specified b e t w e e n

M a n v s . Machine

D u r i n g the pas t year , D o w s tud ied relat ive accuracy of human and m a c h i n e searching—with no cons idera t ion given to relat ive speed. For t h e tes t search, these criteria w e r e es tab l i shed :

• Al l c o m p o u n d s wi th a t least one b e n z e n e ring hav ing two chlorines on it and or tho to each other .

• N o o the r chlor ine a toms on the or thodichloro r ing, a l though the re c o u l d be any n u m b e r of chlorines or b e n z e n e r ings e lsewhere in the mo lecu l e .

• O n the o r t h o d i ch l o ro b en zen e ring, any g r o u p , other than chlor ine , was p e r m i t t e d on any vacan t posi t ion.

• The Human Search. T h e opera to r first s c reened with a p u n c h e d ca rd sorter, select ing more than 1600 cards . Each of these chemicals had two or more chlor ines , a ca rbon- to -ch lor ine b o n d , and a benzene . T h e n the ope ra to r examined each of the 1600 cards—taking about one h o u r and 4 0 minutes—and selected 99 c o m p o u n d s as appl icable .

• The Machine Search. On the 7 0 4 , t w o searches were made , one for o r t h o d i e h l o r o b e n / e n e s and one1 for di ( o r t h o d i e h l o r o h e n z e n e s ) . T h e s e , plus th ree re la ted searches , took six minu tes . The r u n d o w n :

Correct Retrieval

Complete ly characterized Partial ly indeterminate, but known to b e o r t ho Partially indeterminate, with relative

positions not known Incorrect Retrieval ( Fail-Safe ) Failed to Retrieve

Human

<S2 15

13

Machine

9 2 15

2 6 3 0

5

In general , then , any mis takes the c o m p u t e r makes arise Irom h u m a n e r r o r in original cod ing or cause retr ieval of c o m p o u n d s that do not fit the search cr i ter ia . No case of r a n d o m error or failure has been de t ec t ed to d a t e .

T h e h u m a n searcher worked well and rap id ly for a human—at an a v e r a g e ra te of 17 c o m p o u n d s a minu te , she got most of t he des i red c o m p o u n d s and only 2 that w e r e not in t h e right category. However , she over looked the possibility tha t x, y d ich lo robenzenes migh t be o r tho­d i c h l o r o b e n z e n e s . thus missing one g r o u p ol c o m p o u n d s .

F r o m this, w e conclude* tha t search speed is reasonably high and a c e u r a c v is entirelv sat is lactorv.

A U G . 19, 1957 C & E N 9 5

as m a n y a s six different a r r a n g e m e n t s of groups .

T h e fourth a n d most c o m p l e x cr i te­rion is tha t which deals wi th indi rec t and positional a t t a c h m e n t — t w o speci­fied g roups connec ted to t he s a m e (unspecif ied) th i rd g roup . In set t ing up t h e search r e q u i r e m e n t s , w e select a pa i r of g roups (or a pa i r of identi­cal g r o u p s ) , specify the n u m b e r of indirect connect ions b e t w e e n groups ol this t ype tha t m u s t be present and, if desired, t h e posit ional difference b e ­tween the two g r o u p s . Fo r example , if we wish t o specif) that a ni t ro g r o u p and an e the r are a t t ached to t h e s a m e benzene r ing, w e can ensure this con dition by specifying direct connec t ion be tween a nitro a n d a b e n z e n e and b e ­tween an ether a n d a benzene . H o w ­ever, to ove rcome the possibility tha t the nitro and t h e e ther will o be on different benzenes , we specify that t h e ether and the n i t ro are to be a t t a c h e d to t he s ame third g roup . This will not e l iminate the possibil i ty of an occa­sional freak c o m p o u n d be ing a c c e p t e d , but it will reject most of t h e u n a c ­cep tab le c o m p o u n d s . If w e wish t h e ether and nitro g roups to be or tho to each o ther , we specify a posi t ional difference of 1.

Numbering

O n e of the p rob lems tha t th is me thod of analysis h ighl ights is t h e accepted system for n u m b e r i n g posi­tions in c h e l n i c a P c o m p o i i n d s . .In d e ­

cs -o o •" ;-• • •'.;'•; c. .••-vising our method ()f"opy)sitionah''anal-ysis, we have looked at the "iTu in Ber­ing of some of the more c o m m o n chemicals and noted tha t ad jacent a toms are generally assigned consecu­tive n u m b e r s . W h e r e this is t rue , you can de te rmine t he n u m b e r of a toms separat ion by s imply obta in ing the dif­ference be tween the n u m b e r i n g of t he a toms at t h e point of a t t a c h m e n t .

T h i s works perfectly for open chain c o m p o u n d s with s t ra igh t fo rward n u m ­ber ing . Unfor tuna te ly , cer ta in excep­

tions ar ise in single a n d mul t ip le rings. Since yon m u s t start t o number a ring a t a p a r t i c u l a r poin t a n d proceed in one d i r ec t ion , it is obvious that w, t h e last a tom, must b e ad j acen t to 1, t h e first, a n d t h a t the difference b e t w e e n them must b e ( w — 1 ) . Th i s si tuation is agg rava t ed wi th mul t ip le ring sys tems .

T h u s far, we h a v e been a b l e to h a n d l e the p rob l em that occurs most frequently—posit ional relat ionships in six m e m b e r e d r ings. T o d e t e r m i n e w h e t h e r a p a i r of connec t ed g roups are or tho to e a c h other , for example , the c o m p u t e r pe r fo r ins the following s teps :

• D e t e r m i n e s t h e a b s o l u t e difference.

• D e t e r m i n e s w h e t h e r this a b s o l u t e difference is equa l to the desired di\-f e r e n c e (o r tho — 1) . -•-

• If the diflere'nees a re not e q u a l , the a b s o l u t e difference is t aken again and s u b t r a c t e d from • 6.

• T h e difference t h a t now resul ts is taken in its a b s o l u t e form a n d c o m p a r e d t o the requi red difference.

9 If the r e su l t is e q u a l , t h e com­p o u n d is a c c e p t e d ; o therwise , it is re­j ec t ed . T h u s , a b e n z e n e ring d i subs t i -tu ted in the 1 a n d 6 positions w i t h de­sired g roups will be recogn ized as an or tho g roup .

Partially Indeterminate Structures W e often find cases where t h e exact

s t r u c t u r e of a c o m p o u n d is n o t com­p l e t e l y de t e rmined . To enable us to code, these c o m p o u n d s , w e employ two ar t i f ices:

• W h e r e t h e a t t a c h m e n t of t h e g roup t o tin* paren t molecule is u n k n o w n , the code states tha t this is a t t ached to the "9 th" group. O u r n u m b e r i n g system is such that t h e r e is n e v e r a 9th g roup , and, thus , th i s a n o m a l y is recognized.

• W h e r e t h e g roup relations a r e fully k n o w n hut only the positional a t tach­ment is u n c e r t a i n , t h e c o m p o u n d is c o d e d as l o c a t e d in t h e "9th" pos i t ion . This wil l occas ional ly lead to s o m e am­

b igu i ty wi th c o m p o u n d s con t a in ing a 9th posi t ion, b u t , so far, th is h a s not p r o v e n t roub lesome.

W h i l e w e wish to avoid h a v i n g the chemis t scan long lists of c o m p o u n d s to select those that might mee t h i s re­q u i r e m e n t s , w e real ize tha t t h e r e will be nebu lous s i tua t ions w h e r e w e do wan t the chemis t to make the final de­cision. F u r t h e r m o r e , in b a l a n c i n g the two risks—falsely reject ing a val id com­p o u n d and a c c e p t i n g an inval id com­pound—we w i s h to t ake t h e s econd in p re fe rence to the first. C o n s e q u e n t l y , w h e n a m b i g u i t y o r i n d e t e r m i n a n c y arise, our p r o g r a m will a l w a y s select the a m b i g u o u s choice r a t h e r t h a n re­j ec t ing i t—what we call ou r "fail-safe pr inc ip le /* - T h e . finaT decis ion - ' there­fore, is up to t h e chemist .

W h e n e v e r a compound m e e t s all re­q u i r e m e n t s of a search excep t for some that are i n d e t e r m i n a t e , t h e c o m p o u n d is labe l led as i n d e t e r m i n a t e a n d ac­c e p t e d for o u t p u t .

Search Limitations

W e like to refer t o the p r o g r a m w e have wri t ten a s a gene ra l sea rch pro­g r a m . By th i s , we mean tha t it is a s ingle p r o g r a m which can b e modif ied by t h e search r e q u e s t c a rd s so t ha t i t will car ry out most of the s ea r ches tha t are r e q u e s t e d . W i t h our l im i t ed ex­pe r i ence thus far, w e can say t h a t this p r o g r a m can h a n d l e 9 0 *# of t h e searches r e q u e s t e d b y D o w chemis ts .

W h a t a b o u t the o the r 10 rV? T h e s e can be h a n d l e d e i ther b y wr i t ing a s epa ra t e p r o g r a m for special s ea rch ing p rob lems , or, p referab ly , b y modi fy ing the existing p r o g r a m to h a n d l e t h e special s i tua t ion involved. W e have a l r eady successfully e x p e r i m e n t e d with in t roduc ing minor modif icat ions .

A third possibi l i ty : E x p a n d t h e scope of the exis t ing p r o g r a m so tha t it a n s w e r s 99 r /r or 99.9'/r of t he q u e s ­tions asked. W e d o not foresee t h e wr i t ing of a p r o g r a m t h a t wil l t ake care of 100r/< of the p rob lems—chemis t s will a lways b e asking n e w ques t ions .

S o m e of t h e p rob l ems i nc luded in the 10 ' r a re :

• Posi t ions inc lud ing n o n c o n s e c n t i v e n u m b e r i n g .

• D e t e r m i n i n g pos i t ional difference th rough a s e q u e n c e of l inked g roups .

• C o m p o u n d s whose s t r u c t u r e s a rc closed by "cross- l inks."

Presented at the AC'S Miami meet­ing, before the Division of Chemical Literature

Ascher O p l e r is an assoc ia te scientist a t D o w Chemica l ' s w e s t e r n division at P i t t s b u r g , Calif . H e a n d Ted R. Nor ton , now at D o w ' s h o m e office in M i d l a n d , Mich . , o r ig ina ted D o w ' s p r o g r a m of us ing a h igh speed compute r to search th rough chemica l s by s t ruc tu re . I n J u n e of 1956, C&EN pub l i shed a p a p e r c o -a u t h o r e d by O p l e r a n d Nor ton a n d d e s c r i b i n g ea r ly d e v e l o p m e n t of the i r coding sys tem. T h i s pape r p icks up w h e r e t he first left off a n d s u m s ui) two yea r s ' tes t ing exper ience .

9 6 C & E N A U G . 19, 1957

From sucrose or glycerine

and a unique reaction

come two versatile polyols

• . . both new from Dow

Hyprose SP80 shows promise as

a crosslinlcing agent

in polyurethane foams

CH,OC3H4OH

OC,H40H 6csH.OH H

Octakis (2 -hydroxypropy l ) sucrose.

The reaction of propylene oxide with sugar brings you a new and interesting product we call Hyprose* SP80. Technically speaking, it's Octakis (2-hydroxypropyl) sucrose. A unique characteristic of this material is that there is no polvmeric build-up of propylene oxide.

Using Hyprose SP80 as a crosslinking agent, tests show that low-density polyurethane foams can be made with high load-bearing properties and good resiliency. Other studies favor Hyprose SP80 over glycerine or propylene glycol as a plasticizer—particularly in paper, cellophane, and other cellulosic materials. Hvprose SP80 is less vola­tile and less affected by atmospheric moisture changes. Thus, greater permanence on aging and less tendency to lower tensile strength a r e obtained. Also in cellulosic materials, there should b e better dimensional stability.

The emulsifier and detergent field also holds promise, as experimentation delves into the surface-active properties of the fatty acid esters of Hyprose SP80. And judging from preliminary toxicologic^! studies, these esters war­rant further investigation in food and cosmetic applica­tions.

Other uses of Hyprose SP80 as a plasticizer may include materials such as glue, starch, dextrin, phenol-formal­dehyde resins, composition cork products, and particu­larly those products involving a water system.

Hyprin GP25

shows promise as a

plasticizer

Another reaction of propylene oxide has been made with glycerine to form Hyprin* GP25. Like Hyprose SP80, this material (hydroxypropyl glycerine) has no build-up of propylene oxide and as a plasticizer provides advan­tages over glycerine and propylene glycol. It should be especially useful where decreased volatility a n d / o r de ­creased hygroscopicity is desired.

In addition to uses in cellophane, paper and other cel­lulosic products, Hyprin GP25 offers interesting possibili­ties in alkyd resins. It can be esterified with dibasic acids and anhydrides such as phthalic i lhydride. W h e n Hyprin GP25 is used to replace some of the glvcerine in making alkyd resins, greater flexibility in these materials can be expected.

These are only two of a possible series of polvols pro­duced from Dow's wide variety of oxides in this closely controlled reaction with saccharides and polyols.

•TRADEMARK OF THE DOW CHEMICAL COMPANY

For technical bulletins covering Hyprose SP80 and Hyprin GP25, wr i te us wii i iout de 'ay . indicate whether or not you want samples. THE DOW CHEMICAL COMPANY, Midland, Michigan, Technical Service and De­velopment , Department DC 1327A.

YOU CAN DEPEND ON

DQjW

A U G . 19, 1957 C & E N 9 7

D I R E C T O R Y S E C T I O N This section includes: CHEMICALS EXCHANGE — Chemicals, Resins, Gums, Oils, Waxes, Pigments, etc.; EQUIPMENT MART—New Equip­ment, Instruments, and Facilities for Plant and Laboratory; and TECHNI­CAL SERVICES—Consultants, Engi­neering, Testing and Professional Services.

Advertising Rates: Space rate is $30 per inch. Lower rates available on contract basis. An "inch" advertise­ment measures V«" deep on one col­umn. Additional space in even lineal inch units. Maximum Space—4" per Directory per publication. Set ads due 18 days in advance of publication; complete plates—14 days.

E Q U I P M E N T M A R T

TANKoMETER EASURING TANK CONTEf NY DISTANCE AWAY

ISTRUMENT CO. *

FOR MEASURING TANK CONTENTS ANY DISTANCE AWAY

INSTRUMENT CO. 483 GETTY AVENUE. PATERSON,N J.

UNO fO» Buucr IN

$450 ea .

Postpaid

f f NICER 99

Seconds. Slight imperfects of giftware item. Holds ice cubes or chips for hours. Terrific for storage. Dewar use, ice baths. Hundreds already sold to laboratories everywhere.

M A C A L A S T E R BICKNELL CO. 243 Broadway Cambridge, Mass.

foj R E S E A R C H •

• SJ» E C I A L T I E S * 0

: 2005 HOPKINS. ST. BERKELEY 7 / C A L I F .

T E C H N I C A L SERVICES

LaWall & Harrisson Mv K 1921 W*Ht St, NtwUVWl X Pi.

Foods Drug PROBLEMS'

-PhaFmaeologicai: jS^r^

T E C H N I C A L SERVICES

make Spectrogram

Interpretations in

a matter of minutes!

get the / l

iSADTLER/ midget edition /

of standard spectra

You'll get answers in minutes to difficult organic problems by comparing your spectrogram with one or more spectrograms of the SADTLER MIDGET EDITION. Approx. 10.000 spectra printed three to a°page on 8'A " x 11" sheets, indexed by ASTM on IBM cards. Standard edition also available. Write, wire or call.

J LOcust

(4 -0835 ' S A D T L E R RESEARCH LABORATORIES

•TS'IT" VINE ST. J PHILA. 1 , PA.

R E S E A R C H & D E V E L O P M E N T

L A B O R A T O R I E S Toxicology, Engineer­ing, Analyses, Market Re-

N search. Over 100 specialists C I I FOSTER D- SNELL' ,NC-FOSTER D.

2 9 W . 15th St., N . y . 1 1 , N . Y

BJORKSTEN RESEARCH LABORATORIES

SPONSORED INDUSTRIAL RESEARCH IN

PIASTICS COATINGS IAMINAIES ORGANIC SYNTHESIS RADIO ISOTOPES HIGH POLYMERS ADHESIVES

ELECTRONICS LEATHER PAPER GLASS CERAMICS GRAPHIC ARTS BIOCHEMISTRY ELECTROCHEMISTRY

FUELS PROPEUAfMTi METALLURGY FLOTATION HIGH VACUUM

PATEN! SEARCHES ECONOMIC SURVEYS LITERATURE SEARCHES

BRANCH OFFICES WASHINGTON. DC

LABORATORIES & MAIN OFFICE BOX 1 1 75 MADISON. WIS.

SCHWARZKOPF MICROANALYTICAL LABORATORY

Routine AnelysisWithin One Week ANALYSIS OF

BORO and FLUORO COMPOUNDS BY NEW METHODS, ALSO OTHER ANALYSES 56-19 37th A v e , Woodside 77, N. Y.

TELEPHONE HAvemeyer 9-6248. 9-6223

CUSTOM REFINING FACILITIES..

* C o m p l e t e Disti l lat ion Service ( H i g h Temperature-High V a c u u m ) D r u m Lots-Tank Cars

WANTED: * A l l Types o f Crude Mixtures • By-Products , Residues • C o n t a m i n a t e d Solvents

TRULAND CHEMICAL CO., INC. Division of The Trubek Laboratories, Inc.

East Rutherford, New Jersey

LABORATORY SERVICES for the FOOD, FEED, DRUG and

CHEMICAL INDUSTRIES Analyses, Biological Evaluation,

Toxicity Studies, Insecticide Testing and Screening, Flavor Evaluation. Project Research and Consultation

Write for Price Schedule P. O. Box 2217 * Madison 1. Wis.

C H E M I C A L S E X C H A N G E

4-NITR0QUIN0LINE N-0XIDE AVAILABLE IN RESEARCH QUANTITIES

Write for data sheet, prices and listing

of other research chemicals.

BEMOf . ' :Chemigl. Industries, Inc.

33 .RICHDAIE? CAMBRIDGE 40'. MASS

K i logram Quantit ies

PURE PALMITIC ACID N o detec tab le unsaturates

N o C14 N o Cis content Also other high purity chemicals

A p p l i e d Science Laboratories, Inc. 140 N. Barnard S t . . State College, Pa. • AD 8-6282

SODIUM AMIDE (Free Flowing Powder)

THE INDUSTRY STANDARD

FOR OVER A DECADE

COMMERCIAL QUANTITIES

FARCHAN RESEARCH LABS. 609 E. 127th St. Cleveland 8, Ohio

PURINES and other tagged compounds

OF H IGH RADIOPURITY C" IS0TOPESs£|c INC.7035 M""St

•Burbank, Calif.

F L U O R O A R O M A T I C S

Send for Catalog

[PBcPLTCBCB C H E M I C A L C O , t o x n i •• t b c i f o t o . ILL.

AVAILABLE

Aluminum Trimethyl* (ATM) Sp. G . 0 .75 9 8 - 9 9 %

Aluminum Alky ' Halides

Boron Trimethyl

Boron Triethyl

Boron Tributyl

Niobium Halides

Niobium Ox ides

Phosphine (PH3)

Tantalum Halides

Tantalum O x i d e

Custom Synthesis

(Laboratory or Pilot Scale)

ROCKY MOUNTAIN RESEARCH, INC. 6 5 5 B r o a d w a y Building

Denver 3 , Colorado

YOUR ANNOUNCEMENT of new chemicals for sale can carry YOUR MESSAGE to the readers of the leading publication in the chemical process industries.

CHEMICAL & ENGINEERING NEWS

Advertising Office: 430 Park Avenue New York 22, N . Y.